# [PATCH 0/2] connected: add incremental connectivity check 13 messages from 2026-09-14 to 2026-10-06. Participants: Kristofer Karlsson via GitGitGadget, Junio C Hamano, Kristofer Karlsson, Patrick Steinhardt. Thread: https://gitlist.dev/t/66326 ## Kristofer Karlsson via GitGitGadget, 2026-09-14 09:47 Subject: [PATCH 0/2] connected: add incremental connectivity check Message-ID: ``` This series adds an incremental mode for the connectivity check, gated behind transfer.connectivityCheck=incremental (no expected changes unless you opt in). The intent is to solve the problem of the connectivity check slowing down as the number of reachable objects from the boundary grows. It relates to the RFC I sent out earlier: [RFC] check_connected: toward incoming-proportional cost https://lore.kernel.org/git/CAL71e4Nf=-zCrfN7ghEVGq11irajJhtdxYZgKe0Ycux0qs1ZvQ@mail.gmail.com/ Design ====== The verifier runs inside the same rev-list subprocess that check_connected() already spawns, triggered by a new internal flag --verify-trees-incremental. After get_revision() collects the incoming commits, the verifier processes them in topological order (ancestors before descendants). The idea is to keep a set of trusted objects, shared across the incoming commits, that grows over time. We visit the new/untrusted commit trees and do a comparison walk over the trees of their parents. Entries discovered on the trusted parent side are remembered as trusted, which lets later verification skip matching objects and avoid descending into unchanged subtrees. More algorithmic details are in Documentation/technical/connectivity-check.adoc. Benchmarks ========== I'll just mention a short summary here, to avoid repeating what's already in the commit message. The incremental mode is faster than the full mode when there are few commits to verify and when the active object tree is large. In the happy case, the work tracks the changed paths and their comparison trees rather than the full reachable object closure, which substantially reduces the dependence on total repository size. I've seen speedups up to around 20x for the synthetic perf tests. Running against a large real-world repo (3.4 GB boundary closure), the numbers are more dramatic. All timings use rev-list directly with --not HEADN, isolating the tree verification cost from the boundary-finding cost: commits full incr. speedup full RSS incr. RSS 1 1.9s 0.01s 190x 3.4 GB 14 MB 10 1.9s 0.04s 48x 3.4 GB 125 MB 100 1.9s 0.37s 5x 3.4 GB 1.1 GB The full mode takes ~1.9s regardless of commit count because it is dominated by walking the boundary closure. Incremental scales with the number of incoming commits and the paths they touch. Memory follows the same pattern: incremental uses a fraction of the full mode's RSS for small pushes, converging only when many commits are verified. There are also regression cases in the synthetic fixtures. With long incoming histories, the extra parent-tree scans accumulate; in the synthetic fixture incremental is about 1.5x slower at 10000 commits. Per-commit changes have less impact than expected: even when every directory is touched, incremental remains competitive; bypassing the object cache for tree reads likely helps here. I cannot establish how common these regression cases are. In the cases I have tested, however, the regression has remained modest; I have not been able to provoke a substantially larger slowdown. My feeling is that this is an acceptable tradeoff behind the opt-in config, since the target case (small pushes to large repos) sees the largest speedup, while the regression appears with long incoming histories. A safety net for this regression could be to dynamically disable the incremental mode if the number of incoming commits is too large, but this is left out of the initial version to avoid overly speculative code. Deepening fetches currently fall back to the full check because the full check omits --not --all for deepening -- there is no existing-reference boundary at which the walk can stop. An incremental approach is possible here too -- using the old shallow roots as the trusted boundary and walking the deepened ancestry forward -- but that is a separate change and left for future work. Deepening is also less common than regular fetch and receive-pack, where the speedup matters most. Test coverage ============= Most correctness cases in t5412-connectivity-check.sh are run in both full and incremental modes to check semantic equivalence. Selected cases additionally assert trace2 tree/blob counts for the incremental mode, to verify that unchanged portions of the object graph are actually skipped. It covers: * Corruption detection: missing blobs, missing trees, type mismatches, malformed trees (unparseable, mid-tree corruption) * Tree optimization: trace2 assertions confirm unchanged subtrees are skipped, subtree moves, merge parent boundaries * Root commits (no parents -- verifies full tree closure) * Partial clones: missing promised blobs, missing promised trees, verification of local commits * Replacement objects (with and without GIT_NO_REPLACE_OBJECTS) * Shallow boundaries * Deepening fetches (falls back to full check) * Integration: real push, fetch, and clone Most tests call git rev-list directly with the appropriate flags; integration tests exercise the full check_connected() path through push, fetch, and clone. Alternatives considered ======================= My first prototype ran the verifier in-process inside connected.c. This required a second rev-list subprocess just for boundary finding, _nofetch variants of several object-reading functions to prevent lazy fetches in partial clones, explicit shallow-file plumbing, and careful avoidance of die() in all code paths reachable from the verifier. The result worked but was fragile and touched many files. Moving the verifier into the rev-list subprocess eliminated all of those problems: in partial clones the existing --exclude-promisor-objects handling already disables lazy fetching, die() is isolated by the process boundary, shallow and replacement semantics are established before the verifier runs, and error routing comes for free via stderr. So while I liked the idea of being less reliant on checking within a subprocess, making that work ended up being a lot more complex. Next steps ========== This series only addresses tree verification; the other significant cost is finding the commit boundary, especially for repos with many refs. I already have some prototypes for optimizing that too, and if this ends up landing, that would be something I would start polishing up. Thanks, Kristofer Kristofer Karlsson (2): Documentation: describe connectivity checking connected: add incremental connectivity check via rev-list Documentation/config/transfer.adoc | 20 + Documentation/rev-list-options.adoc | 6 + .../technical/connectivity-check.adoc | 243 +++++++ Makefile | 1 + builtin/rev-list.c | 18 + connected.c | 24 + meson.build | 1 + t/meson.build | 1 + ...enerate-repo-p5412-connectivity-check.perl | 44 ++ t/perf/p5412-connectivity-check.sh | 92 +++ t/t5412-connectivity-check.sh | 655 ++++++++++++++++++ tree-verify.c | 306 ++++++++ tree-verify.h | 15 + 13 files changed, 1426 insertions(+) create mode 100644 Documentation/technical/connectivity-check.adoc create mode 100644 t/perf/generate-repo-p5412-connectivity-check.perl create mode 100755 t/perf/p5412-connectivity-check.sh create mode 100755 t/t5412-connectivity-check.sh create mode 100644 tree-verify.c create mode 100644 tree-verify.h base-commit: 47ce80527c56f462cb97db4ca8125342204d3783 Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2211%2Fspkrka%2Ftree-diff-connectivity-v1-clean-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2211/spkrka/tree-diff-connectivity-v1-clean-v1 Pull-Request: https://github.com/gitgitgadget/git/pull/2211 -- gitgitgadget ``` ## Kristofer Karlsson via GitGitGadget, 2026-09-14 09:47 Subject: [PATCH 1/2] Documentation: describe connectivity checking Message-ID: In-Reply-To: ``` From: Kristofer Karlsson Add Documentation/technical/connectivity-check.adoc describing the connectivity invariant and the full connectivity check. Signed-off-by: Kristofer Karlsson --- .../technical/connectivity-check.adoc | 109 ++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 Documentation/technical/connectivity-check.adoc diff --git a/Documentation/technical/connectivity-check.adoc b/Documentation/technical/connectivity-check.adoc new file mode 100644 index 0000000000..d20bff6af6 --- /dev/null +++ b/Documentation/technical/connectivity-check.adoc @@ -0,0 +1,109 @@ +Connectivity checking +===================== + +After receiving new objects via fetch, push (receive-pack), clone, +or bundle, Git verifies that the new reference tips do not leave +the repository in a state where reachable objects are missing. +This verification is called the connectivity check. + +Connectivity invariant +---------------------- + +A repository is connected when every object reachable from its +references is available locally (with exceptions noted below). + +The connectivity check maintains this invariant when references +are updated. It trusts the existing connected state and verifies +that the new reference tips do not introduce references to +unavailable objects. Verification is permitted to stop when it +reaches objects already reachable from trusted existing +references, since their closure is already connected. These +trusted references include local references and references from +alternate object stores. + +Without this check, a truncated or corrupted transfer could leave +a repository in a state where later history walks encounter +missing objects. + +Exceptions +~~~~~~~~~~ + +Gitlink entries (submodule references) are excluded from +connectivity checking. Their target objects belong to a separate +repository. + +In partial clones, objects promised by a promisor remote are +accepted as connected without requiring local existence. The +check excludes promisor objects from traversal so that it does +not trigger on-demand fetches for them. + +Full connectivity check +----------------------- + +`check_connected()` (see `connected.c`) normally performs the +connectivity check using a `rev-list` subprocess, feeding the +new reference tips via stdin. A normal invocation is roughly: + + git rev-list --objects --stdin --not --all --quiet + --alternate-refs [--exclude-promisor-objects] + +When promisor remotes are configured, `check_connected()` first +attempts a fast path based on promisor packfiles. If it falls +back to the `rev-list` check, `--exclude-promisor-objects` is +added so that the traversal does not trigger on-demand fetches. + +Consider the following graph after a fetch, where all reference +tips point directly to commits. For simplicity, only local +references appear on the already-connected side; alternate refs +play the same role. N3 is a merge commit: + + /-------------L2 + / + C1---B1---C2---B2-----L1 + \ \ + N1 N3---T2 + \ / + N2-----------T1 + + L1, L2: local refs + T1, T2: incoming tips (new refs) + N1, N2, N3: incoming commits (N3 is a merge) + B1, B2: boundary commits (already connected) + C1, C2: already connected (but not boundary) + +The incoming set is the commits reachable from the incoming +tips but not from the already-connected side. Boundary commits +are the already-connected commits at the edge of that set. Here +B1 is an ancestor of B2, which happens when incoming branches +fork at different depths in the existing history. + +The check proceeds in three phases: + +1. Walk from the incoming tips (T1, T2) against the trusted + refs (L1, L2) to find the incoming set ({N1, N2, N3, T1, T2}). + +2. Walk the trees of the boundary commits (B1, B2) and mark + those objects uninteresting. These trees are already trusted + because their commits are on the already-connected side. + +3. Walk the trees of each incoming commit and verify that every + referenced object is connected, stopping at objects already + marked uninteresting in phase 2. + +Deepening fetches +~~~~~~~~~~~~~~~~~ + +For deepening fetches (where the shallow boundary moves), the +full check omits `--not --all`. There is no existing-reference +boundary at which the walk can stop. Instead, traversal follows +the effective shallow boundary supplied for the deepened +repository. The new content may be below the old shallow +boundary even when the tips themselves have not changed. + +Non-commit tips +~~~~~~~~~~~~~~~ + +When a new reference points to a non-commit object, such as a +tag, tree, or blob, that object is not part of the commit walk. +These non-commit tips are handled by the subsequent object +traversal. -- gitgitgadget ``` ## Kristofer Karlsson via GitGitGadget, 2026-09-14 09:47 Subject: [PATCH 2/2] connected: add incremental connectivity check via rev-list Message-ID: In-Reply-To: ``` From: Kristofer Karlsson The full connectivity check uses rev-list to find commits reachable from the incoming tips but not from the already-connected side, then walks their object closure. Commit traversal stops at the connectivity boundary, but trees and blobs reachable from that boundary still need to be walked so they can be marked uninteresting, allocating a struct object for each one. On repositories where the boundary commits have large trees, the connectivity check for small incoming changes visits and tracks more objects than needed. Add an alternative connectivity check that verifies incoming commits incrementally against their parents. The verifier processes incoming commits with ancestors first and compares each new tree against its trusted parent trees. Entries already seen on the trusted side are skipped by OID, so unchanged subtrees need not remain at the same path to be recognized. Changed subtrees are recursively compared against same-path parent subtrees, and new subtrees without a comparison base are verified from scratch. See Documentation/technical/connectivity-check.adoc for the trust invariants and detailed algorithm. The incremental check runs as an internal --verify-trees-incremental mode in rev-list. After the normal revision walk identifies the incoming commits, the verifier consumes them before the usual object traversal; any pending non-commit tips are still handled by the existing traversal. Partial-clone semantics are preserved: objects promised by a promisor remote are accepted as connected, and on-demand fetching is prevented by excluding promisor objects from traversal. The new mode is selected by transfer.connectivityCheck=incremental, with full remaining the default. Deepening fetches fall back to the full check because they do not have the normal existing-reference boundary, and traversal instead follows the effective shallow boundary. p5412 results (median of 3), scaling one dimension at a time. Each fixture is a repository with a flat tree of many directories containing 100 files each. The incoming set is a chain of commits on top of the existing history, with each commit changing files in different directories round-robin. The three axes vary the total repository tree size, the number of incoming commits, and the number of files changed per incoming commit. Scaling tree size (10 incoming commits, 10 files/commit): files full incr. full/incr 5K 0.01s 0.01s 1.0x 50K 0.04s 0.01s 4.0x 200K 0.15s 0.01s 15.0x 800K 0.61s 0.03s 20.3x The full mode must walk the trees of boundary commits, which grows with overall tree size. Incremental still scans the root trees, but avoids descending into unchanged subtrees, so it grows much more slowly with repository size. Scaling incoming commit count (200K files, 10 files/commit): commits full incr. full/incr 1 0.14s 0.01s 14.0x 10 0.15s 0.01s 15.0x 100 0.19s 0.05s 3.8x 500 0.32s 0.27s 1.2x 3000 1.23s 1.52s 0.8x 5000 1.88s 2.43s 0.8x 10000 3.72s 5.36s 0.7x With many commits the per-commit overhead of scanning both the new and parent root trees accumulates and incremental becomes slower. Breakeven is between 500 and 3000 commits and the ratio stabilizes near 0.7x for this fixture. Scaling files per incoming commit (200K files, 10 commits): files/commit full incr. full/incr 1 0.14s 0.01s 14.0x 10 0.15s 0.01s 15.0x 100 0.16s 0.04s 4.0x 500 0.23s 0.14s 1.6x 1000 0.34s 0.28s 1.2x 2000 0.70s 0.63s 1.1x Breakeven is around 1000 files/commit. At 2000 files/commit (every directory touched), incremental remains slightly faster; bypassing the object cache for tree reads likely helps here. For small repositories both modes are fast enough that the difference is difficult to measure reliably. Selected peak RSS measurements from the same fixtures: case full incr. ratio 200K files, 10 commits 31 MB 12 MB 0.4x 800K files, 10 commits 110 MB 26 MB 0.2x 200K files, 5000 commits 155 MB 151 MB 1.0x Incremental uses substantially less memory when it can prune most of the boundary tree walk. In the long-history case the two modes visit similar object sets and memory converges. The regression cases in the CPU benchmarks are in wall-clock time rather than memory, primarily from scanning some trees more than once. Signed-off-by: Kristofer Karlsson --- Documentation/config/transfer.adoc | 20 + Documentation/rev-list-options.adoc | 6 + .../technical/connectivity-check.adoc | 134 ++++ Makefile | 1 + builtin/rev-list.c | 18 + connected.c | 24 + meson.build | 1 + t/meson.build | 1 + ...enerate-repo-p5412-connectivity-check.perl | 44 ++ t/perf/p5412-connectivity-check.sh | 92 +++ t/t5412-connectivity-check.sh | 655 ++++++++++++++++++ tree-verify.c | 306 ++++++++ tree-verify.h | 15 + 13 files changed, 1317 insertions(+) create mode 100644 t/perf/generate-repo-p5412-connectivity-check.perl create mode 100755 t/perf/p5412-connectivity-check.sh create mode 100755 t/t5412-connectivity-check.sh create mode 100644 tree-verify.c create mode 100644 tree-verify.h diff --git a/Documentation/config/transfer.adoc b/Documentation/config/transfer.adoc index f1ce50f4a6..b9939d3bde 100644 --- a/Documentation/config/transfer.adoc +++ b/Documentation/config/transfer.adoc @@ -1,3 +1,23 @@ +transfer.connectivityCheck:: + Choose which algorithm to use for the connectivity check + performed during object transfer operations such as + linkgit:git-fetch[1] and linkgit:git-receive-pack[1]. + The connectivity check verifies that all objects reachable + from the incoming tips are available locally or, in a partial + clone, promised by a promisor remote. + The variants are as follows: ++ +-- +`full` (default);; + Walk the full object closure of the boundary commits. +`incremental`;; + Verify incoming commits by diffing their trees against parent + trees, recursively descending only into entries that differ. + The largest benefits occur when incoming commits change a + small fraction of a large tree closure. + Falls back to `full` for deepening fetches. +-- + transfer.credentialsInUrl:: A configured URL can contain plaintext credentials in the form `://:@/`. You may want diff --git a/Documentation/rev-list-options.adoc b/Documentation/rev-list-options.adoc index fd831f0ec6..7964b691c4 100644 --- a/Documentation/rev-list-options.adoc +++ b/Documentation/rev-list-options.adoc @@ -1089,6 +1089,12 @@ we cannot get their Object ID though, an error will be raised. stronger than `--missing=allow-promisor` because it limits the traversal, rather than just silencing errors about missing objects. + +`--verify-trees-incremental`:: + (For internal use only.) Verify tree connectivity + incrementally by comparing each commit's tree against its + parent trees. Used by `check_connected()` when + `transfer.connectivityCheck` is set to `incremental`. endif::git-rev-list[] `--no-walk[=(sorted|unsorted)]`:: diff --git a/Documentation/technical/connectivity-check.adoc b/Documentation/technical/connectivity-check.adoc index d20bff6af6..0a8f370546 100644 --- a/Documentation/technical/connectivity-check.adoc +++ b/Documentation/technical/connectivity-check.adoc @@ -107,3 +107,137 @@ When a new reference points to a non-commit object, such as a tag, tree, or blob, that object is not part of the commit walk. These non-commit tips are handled by the subsequent object traversal. + +Incremental connectivity check +------------------------------ + +The incremental mode, selected by +`transfer.connectivityCheck=incremental`, avoids traversing the +full tree walk of the boundary commits. Instead, it verifies +each incoming commit's tree against the already-trusted trees of +its parents. + +Trust model +~~~~~~~~~~~ + +A tree is trusted when its transitive object closure is known to +be connected. Trees reachable from commits on the +already-connected side of the boundary are therefore trusted. + +Incoming commits are processed with ancestors before descendants. +Once an incoming commit's tree has been verified, it is trusted +and can be used as a comparison base for later descendants. + +This gives an inductive correctness argument: every parent of the +commit currently being verified is either already connected or is +an earlier incoming commit whose tree has already been verified. + +Tree states +~~~~~~~~~~~ + +The verifier tracks tree OIDs in three states: + +untrusted:: + The tree has not yet been established as connected. This + is the implicit state of an OID not present in the state + map. + +trusted:: + The tree is known to have a connected transitive closure, + but its direct entries have not yet been published into the + verifier's trusted object sets. + +expanded:: + The tree is trusted and its direct non-gitlink entries + have also been published into the trusted object sets. + +State transitions are monotonic: a tree may move from untrusted +to trusted to expanded, but never backwards. An untrusted tree +that is successfully verified goes directly to expanded. + +Blobs require only trusted/untrusted state: a blob becomes +trusted when it is found in a trusted tree or when its existence +and type have been verified directly. + +The trusted/expanded distinction is an optimization. An expanded +parent does not need to be reread merely to publish entries that +are already trusted, though it may still be read when same-path +subtree bases are needed for recursive comparison. + +Algorithm +~~~~~~~~~ + +At a high level: + + verify(commits): + sort topologically (ancestors first) + for each commit: + mark parent root trees as trusted + verify_tree(commit.tree, parent root trees) + + verify_tree(tree, base_trees): + if tree already trusted: return + read tree, collect entries not already trusted + for each available base tree: + publish its entries as trusted + record same-path subtrees as bases + for each collected entry: + if now trusted: skip + if blob: verify blob connectivity and type + if tree: verify_tree(entry, its recorded bases) + mark tree as expanded + +The important ordering within `verify_tree` is that entries from +the new tree are collected before the base trees are scanned, but +are processed only afterwards. Trust learned from any base can +therefore eliminate work before recursive verification begins. + +Same-path parent subtrees are passed down as comparison bases +during recursive descent. If no comparison base is available, +the new subtree is verified from scratch. + +Worked example +~~~~~~~~~~~~~~ + +Consider a commit that changes one file under `lib/` and moves an +unchanged subtree from `src/` to `dev/`: + + Parent tree New tree + +-- src/ (aaa) +-- dev/ (aaa) + +-- lib/ (bbb) +-- lib/ (ccc) + +-- foo.c (ddd) +-- foo.c (ddd) + +-- bar.c (eee) +-- bar.c (fff) + +Scanning the parent makes `aaa` trusted even though it moved from +`src/` to `dev/`, so that subtree is skipped. The changed `ccc` +subtree is compared against its same-path parent `bbb`; scanning +`bbb` makes `ddd` and `eee` trusted, leaving only the new `fff` +blob to be checked. + +This illustrates two properties: + +* Trust is OID-based rather than path-based. An unchanged subtree + is recognized after a move. + +* Same-path parent subtrees provide recursive comparison bases. + These bases improve pruning efficiency but are not required for + correctness; a new subtree can always be verified from scratch. + +Multiple parents +~~~~~~~~~~~~~~~~ + +For a merge commit, root trees from all parents are comparison +bases. When several parents contain a same-path subtree, each +matching subtree is collected as a recursive comparison base. + +Entries published from any trusted parent become globally trusted, +so a matching tree or blob entry present in any parent can be +skipped while verifying the merge tree. + +Missing comparison bases +~~~~~~~~~~~~~~~~~~~~~~~~ + +A promised base tree may not be locally available for comparison. +In that case the verifier skips that base and verifies the new +subtree without it. The missing comparison can reduce pruning but +does not affect correctness. diff --git a/Makefile b/Makefile index d4b775953d..aa5b4e2b84 100644 --- a/Makefile +++ b/Makefile @@ -1357,6 +1357,7 @@ LIB_OBJS += trailer.o LIB_OBJS += transport-helper.o LIB_OBJS += transport.o LIB_OBJS += tree-diff.o +LIB_OBJS += tree-verify.o LIB_OBJS += tree-walk.o LIB_OBJS += tree.o LIB_OBJS += unpack-trees.o diff --git a/builtin/rev-list.c b/builtin/rev-list.c index 6b596231ab..7741fdec9f 100644 --- a/builtin/rev-list.c +++ b/builtin/rev-list.c @@ -28,6 +28,7 @@ #include "commit-reach.h" #include "quote.h" #include "strbuf.h" +#include "tree-verify.h" struct rev_list_info { struct rev_info *revs; @@ -706,6 +707,7 @@ int cmd_rev_list(int argc, int bisect_find_all = 0; int use_bitmap_index = 0; int filter_provided_objects = 0; + int verify_trees_incremental = 0; const char *show_progress = NULL; int ret = 0; @@ -748,6 +750,8 @@ int cmd_rev_list(int argc, if (!strcmp(arg, "--exclude-promisor-objects")) { repo->fetch_if_missing = 0; revs.exclude_promisor_objects = 1; + } else if (!strcmp(arg, "--verify-trees-incremental")) { + verify_trees_incremental = 1; } else if (skip_prefix(arg, "--missing=", &arg)) { parse_missing_action_value(repo, arg); } else if (!strcmp(arg, "-z")) { @@ -822,6 +826,8 @@ int cmd_rev_list(int argc, if (!strcmp(arg, "--exclude-promisor-objects")) continue; /* already handled above */ + if (!strcmp(arg, "--verify-trees-incremental")) + continue; /* already handled above */ if (skip_prefix(arg, "--missing=", &arg)) continue; /* already handled above */ @@ -935,6 +941,18 @@ int cmd_rev_list(int argc, prepare_maximal_independent(&revs); + if (verify_trees_incremental) { + struct commit *commit; + struct commit_list *new_commits = NULL; + + while ((commit = get_revision(&revs)) != NULL) + commit_list_insert(commit, &new_commits); + + verify_commits_incremental(repo, &new_commits, + revs.exclude_promisor_objects); + commit_list_free(new_commits); + } + if (revs.tree_objects) mark_edges_uninteresting(&revs, show_edge, 0); diff --git a/connected.c b/connected.c index 929b9bd28d..e3dcd8e2b0 100644 --- a/connected.c +++ b/connected.c @@ -1,6 +1,7 @@ #define USE_THE_REPOSITORY_VARIABLE #include "git-compat-util.h" +#include "config.h" #include "gettext.h" #include "hex.h" #include "odb.h" @@ -67,6 +68,26 @@ static int check_connected_promisor(oid_iterate_fn fn, return 1; } +static int incremental_check_applicable(struct check_connected_options *opt) +{ + const char *algorithm = NULL; + + if (repo_config_get_string_tmp(the_repository, + "transfer.connectivitycheck", + &algorithm)) + return 0; + if (!strcasecmp(algorithm, "full")) + return 0; + if (strcasecmp(algorithm, "incremental")) + die(_("unknown transfer.connectivityCheck algorithm '%s'"), + algorithm); + + if (opt->is_deepening_fetch) + return 0; + + return 1; +} + /* * If we feed all the commits we want to verify to this command * @@ -133,6 +154,9 @@ int check_connected(oid_iterate_fn fn, void *cb_data, if (opt->progress) strvec_pushf(&rev_list.args, "--progress=%s", _("Checking connectivity")); + if (incremental_check_applicable(opt)) + strvec_push(&rev_list.args, + "--verify-trees-incremental"); rev_list.git_cmd = 1; if (opt->env) diff --git a/meson.build b/meson.build index 0a95d90d21..d94dedc26c 100644 --- a/meson.build +++ b/meson.build @@ -562,6 +562,7 @@ libgit_sources = [ 'transport-helper.c', 'transport.c', 'tree-diff.c', + 'tree-verify.c', 'tree-walk.c', 'tree.c', 'unpack-trees.c', diff --git a/t/meson.build b/t/meson.build index 7f53cca7d1..19a8246c44 100644 --- a/t/meson.build +++ b/t/meson.build @@ -652,6 +652,7 @@ integration_tests = [ 't5409-colorize-remote-messages.sh', 't5410-receive-pack.sh', 't5411-proc-receive-hook.sh', + 't5412-connectivity-check.sh', 't5500-fetch-pack.sh', 't5501-fetch-push-alternates.sh', 't5502-quickfetch.sh', diff --git a/t/perf/generate-repo-p5412-connectivity-check.perl b/t/perf/generate-repo-p5412-connectivity-check.perl new file mode 100644 index 0000000000..9546996280 --- /dev/null +++ b/t/perf/generate-repo-p5412-connectivity-check.perl @@ -0,0 +1,44 @@ +#!/usr/bin/perl +# +# Generate a fast-import stream for p5412 connectivity check benchmarks. +# +# Usage: generate-repo-p5412-connectivity-check.perl +# [] [] +# +# Creates one initial commit with dirs*files_per_dir files, then +# additional commits each modifying +# files in directories chosen round-robin from 1... + +use strict; +use warnings; + +my ($nd, $nf, $nc, $hot, $fpc) = @ARGV; +$hot = $nd if !$hot || $hot > $nd; +$fpc = 1 if !$fpc; + +sub data { + printf "data %d\n%s\n", length($_[0]), $_[0]; +} + +# Initial tree: one commit with nd*nf files. +printf "commit refs/heads/main\n"; +printf "committer perf now\n"; +data("initial"); +for my $d (1..$nd) { + for my $f (1..$nf) { + printf "M 100644 inline d-%04d/f-%03d\n", $d, $f; + data(sprintf "%03d%03d", $d, $f); + } +} + +# Subsequent commits (auto-chained by fast-import). +for my $i (1..$nc) { + printf "commit refs/heads/main\n"; + printf "committer perf now\n"; + data(sprintf "change-%03d", $i); + for my $j (0..$fpc-1) { + my $d = (($i + $j) % $hot) + 1; + printf "M 100644 inline d-%04d/f-001\n", $d; + data(sprintf "c%d-%d", $i, $j); + } +} diff --git a/t/perf/p5412-connectivity-check.sh b/t/perf/p5412-connectivity-check.sh new file mode 100755 index 0000000000..827643a847 --- /dev/null +++ b/t/perf/p5412-connectivity-check.sh @@ -0,0 +1,92 @@ +#!/bin/sh + +test_description='performance of connectivity check modes + +Compare the default and incremental rev-list connectivity modes +directly, avoiding pack transfer noise. + +Each repository has a flat tree of many directories with 100 files +in each. Three axes are scaled independently: tree size, commit +count, and files changed per commit.' + +. ./perf-lib.sh + +test_perf_fresh_repo + +generate="$TEST_DIRECTORY/perf/generate-repo-p5412-connectivity-check.perl" + +# $1=dirs $2=files_per_dir $3=commits $4=hot_dirs (optional, default=all) +# $5=files_per_commit (optional, default=1) +test_perf_conn () { + local nd="$1" nf="$2" nc="$3" hot="${4:-$1}" fpc="${5:-1}" + local total=$(($nd * $nf)) + local name="repo-${nd}d-${nf}f-${nc}c-${hot}h-${fpc}fpc" + local label="${total} files, ${nc} commits" + if test "$hot" -lt "$nd" + then + label="$label (${hot} hot dirs)" + fi + if test "$fpc" -gt 1 + then + label="$label (${fpc} files/commit)" + fi + + test_expect_success "setup $label" ' + if test -d '"$name"' + then + true + else + git init '"$name"' && + "$PERL_PATH" '"$generate"' '"$nd"' '"$nf"' '"$nc"' '"$hot"' '"$fpc"' | + git -C '"$name"' fast-import --date-format=now --quiet && + ( + cd '"$name"' && + git rev-parse main~'"$nc"' >../'"${name}"'_old && + git rev-parse main >../'"${name}"'_new && + git update-ref refs/heads/main \ + $(cat ../'"${name}"'_old) && + git repack -ad && + git config gc.auto 0 + ) + fi + ' + + test_perf "$label (full)" ' + cat '"${name}"'_new | + git -C '"$name"' rev-list \ + --objects --stdin --not --all --quiet \ + --exclude-promisor-objects + ' + + test_perf "$label (incremental)" ' + cat '"${name}"'_new | + git -C '"$name"' rev-list --verify-trees-incremental \ + --objects --stdin --not --all --quiet \ + --exclude-promisor-objects + ' +} + +# Scaling tree size (10 commits, 10 files/commit). +test_perf_conn 50 100 10 50 10 +test_perf_conn 500 100 10 500 10 +test_perf_conn 2000 100 10 2000 10 +test_perf_conn 8000 100 10 8000 10 + +# Scaling commit count (200K files, 10 files/commit). +test_perf_conn 2000 100 1 2000 10 +test_perf_conn 2000 100 10 2000 10 +test_perf_conn 2000 100 100 2000 10 +test_perf_conn 2000 100 500 2000 10 +test_perf_conn 2000 100 3000 2000 10 +test_perf_conn 2000 100 5000 2000 10 +test_perf_conn 2000 100 10000 2000 10 + +# Scaling files per commit (200K files, 10 commits). +test_perf_conn 2000 100 10 2000 1 +test_perf_conn 2000 100 10 2000 10 +test_perf_conn 2000 100 10 2000 100 +test_perf_conn 2000 100 10 2000 500 +test_perf_conn 2000 100 10 2000 1000 +test_perf_conn 2000 100 10 2000 2000 + +test_done diff --git a/t/t5412-connectivity-check.sh b/t/t5412-connectivity-check.sh new file mode 100755 index 0000000000..e276085e83 --- /dev/null +++ b/t/t5412-connectivity-check.sh @@ -0,0 +1,655 @@ +#!/bin/sh + +test_description='connectivity check (transfer.connectivityCheck)' +GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main +export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME + +. ./test-lib.sh + +test_oid_cache <<-\EOF +missing sha1:0000000000000000000000000000000000000001 +missing sha256:0000000000000000000000000000000000000000000000000000000000000001 +EOF + +set_connectivity_check () { + git -C "$1" config transfer.connectivityCheck "$2" +} + +# Run a connectivity check via rev-list directly. Uses $mode +# (set by the enclosing for-loop) to choose full or incremental. +check_connected () { + flags= && + if test "$mode" = incremental + then + flags=--verify-trees-incremental + fi && + printf '%s\n' "$@" | + git rev-list $flags \ + --objects --stdin --not --all --quiet \ + --exclude-promisor-objects +} + +# Run git with a temporary index, leaving the real index untouched. +tmpgit () { + GIT_INDEX_FILE=.git/tmp-idx git "$@" +} + +# Create a commit with one file changed, without modifying HEAD, +# index, or worktree. Prints the new commit OID on stdout. +# Usage: commit_with_change +commit_with_change () { + new_blob=$(echo "$3" | git hash-object -w --stdin) && + tmpgit read-tree "$1" && + tmpgit update-index --replace \ + --cacheinfo "100644,$new_blob,$2" && + new_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + git commit-tree "$new_tree" -p "$1" -m "modify $2" +} + +# Check OIDs and optionally verify trace2 counts. +# Usage: check_connected_trace ... +# An empty string for or skips that assertion. +check_connected_trace () { + trace_file=$1 trees=$2 blobs=$3 && + shift 3 && + test_env GIT_TRACE2_EVENT="$(pwd)/$trace_file" \ + check_connected "$@" && + if test "$mode" != incremental + then + return + fi && + if test -n "$trees" + then + test_trace2_data_singular connectivity trees_loaded "$trees" \ + <"$trace_file" + fi && + if test -n "$blobs" + then + test_trace2_data_singular connectivity blobs_checked "$blobs" \ + <"$trace_file" + fi +} + +# Shared setup: a repo with several root-level files and nested dirs. +# The unchanged/ subtree (10 dirs x 10 files = 100 blobs, 11 trees) +# acts as a canary: any test asserting small tree/blob counts would +# fail dramatically if incremental accidentally walked into it. + +test_expect_success 'setup main repo' ' + git init main-repo && + ( + cd main-repo && + for i in $(test_seq 1 5) + do + echo "file $i" >"file-$i.txt" || return 1 + done && + git add file-*.txt && + git commit -m "initial" && + + mkdir -p a/b/c && + echo deep >a/b/c/deep.txt && + echo other >a/other.txt && + git add a/b/c/deep.txt a/other.txt && + git commit -m "add nested dirs" && + + for i in $(test_seq 1 10) + do + d="unchanged/dir-$i" && + mkdir -p "$d" && + for j in $(test_seq 1 10) + do + echo "$i $j" >"$d/file-$j.txt" || return 1 + done + done && + git add unchanged/ && + git commit -m "add unchanged canary subtree" + ) +' + +test_expect_success 'setup replacement object repo' ' + git init replace-test && + ( + cd replace-test && + + test_commit --no-tag original file.txt && + original=$(git rev-parse HEAD) && + orig_blob=$(git rev-parse HEAD:file.txt) && + + # Orphan replacement commit with a different tree + replacement_tree=$(echo replaced | git hash-object -w --stdin | + xargs -I{} git mktree <<-EOF + 100644 blob {} file.txt + EOF + ) && + replacement=$(git commit-tree -m "replacement" \ + "$replacement_tree") && + + git replace "$original" "$replacement" && + + # Remove the original blob so only the replacement + # tree is complete. + rm .git/objects/$(test_oid_to_path "$orig_blob") && + + # Drop branch and HEAD so --not --all does not + # exclude the original commit. + git update-ref -d refs/heads/main && + git update-ref -d HEAD && + + echo "$original" >.git/test-oid + ) +' + +missing_oid=$(test_oid missing) +original_oid=$(cat replace-test/.git/test-oid) + +for mode in full incremental +do + +# Corruption detection: craft broken object graphs and verify detection. +# All tests use main-repo without modifying its refs or worktree. + +test_expect_success "$mode: rejects commit with missing blob" ' + ( + cd main-repo && + bad_tree=$(printf "100644 blob ${missing_oid}\tfile.txt\n" | + git mktree --missing) && + bad_commit=$(git commit-tree "$bad_tree" -p HEAD -m "bad") && + test_expect_code 128 check_connected "$bad_commit" 2>err && + test_grep "missing blob object" err + ) +' + +test_expect_success "$mode: rejects commit with missing subtree" ' + ( + cd main-repo && + bad_tree=$(printf "40000 tree ${missing_oid}\tdir\n" | + git mktree --missing) && + bad_commit=$(git commit-tree "$bad_tree" -p HEAD -m "bad") && + test_expect_code 128 check_connected "$bad_commit" 2>err && + test_grep "bad tree object" err + ) +' + +test_expect_success "$mode: verifies direct tree tip" ' + ( + cd main-repo && + bad_tree=$(printf "100644 blob ${missing_oid}\tfile.txt\n" | + git mktree --missing) && + test_expect_code 128 check_connected "$bad_tree" 2>err && + test_grep "missing blob object" err + ) +' + +test_expect_success "$mode: verifies direct blob tip" ' + ( + cd main-repo && + blob_oid=$(echo "hello" | git hash-object -w --stdin) && + check_connected "$blob_oid" + ) +' + +test_expect_success "$mode: rejects missing direct blob tip" ' + ( + cd main-repo && + test_expect_code 128 check_connected \ + "$missing_oid" 2>err + ) +' + +test_expect_success PERL_TEST_HELPERS \ + "$mode: rejects blob OID reused as tree entry" ' + ( + cd main-repo && + + blob_oid=$(git rev-parse HEAD:file-1.txt) && + bin_oid=$(echo "$blob_oid" | hex2oct) && + + bad_tree=$(printf "40000 subdir\0$bin_oid" | + git hash-object -t tree -w --stdin) && + bad_commit=$(git commit-tree -p HEAD -m "child" "$bad_tree") && + + test_expect_code 128 check_connected "$bad_commit" 2>err && + test_grep "not a tree" err + ) +' + +test_expect_success PERL_TEST_HELPERS \ + "$mode: rejects tree OID reused as blob entry" ' + ( + cd main-repo && + + tree_oid=$(git rev-parse HEAD:a) && + bin_oid=$(echo "$tree_oid" | hex2oct) && + + bad_tree=$(printf "100644 fakefile\0$bin_oid" | + git hash-object -t tree -w --stdin) && + bad_commit=$(git commit-tree -p HEAD -m "child" "$bad_tree") && + + test_expect_code 128 check_connected "$bad_commit" 2>err && + test_grep "not a blob" err + ) +' + +test_expect_success "$mode: checks multiple tips" ' + ( + cd main-repo && + c1=$(commit_with_change HEAD file-1.txt "tip-a") && + c2=$(commit_with_change HEAD file-2.txt "tip-b") && + git tag -a -m "tagged" multi-tag "$c1" && + tag_oid=$(git rev-parse multi-tag) && + git tag -d multi-tag && + check_connected "$c2" "$tag_oid" + ) +' + +# Tree-diff optimization: verify trace2 counts. + +test_expect_success "$mode: handles root commit (no parents)" ' + ( + cd main-repo && + blob_oid=$(echo "root-content" | git hash-object -w --stdin) && + tree_oid=$(printf "100644 blob %s\tfile.txt\n" \ + "$blob_oid" | git mktree) && + root_oid=$(git commit-tree "$tree_oid" -m "root") && + + # No parent trees, so the full tree is verified. + # 1 tree loaded (root), 1 blob checked. + check_connected_trace trace-root.txt 1 1 "$root_oid" + ) +' + +test_expect_success "$mode: handles single file change" ' + ( + cd main-repo && + oid=$(commit_with_change HEAD file-1.txt "changed") && + + # 2 trees loaded (new root + parent root), 1 blob checked. + check_connected_trace trace-flat.txt 2 1 "$oid" + ) +' + +test_expect_success "$mode: handles nested change" ' + ( + cd main-repo && + oid=$(commit_with_change HEAD a/b/c/deep.txt "deep-changed") && + # 4 new trees + 4 parent trees = 8 loaded, 1 blob checked. + check_connected_trace trace-nested.txt 8 1 "$oid" + ) +' + +test_expect_success "$mode: handles change-then-revert" ' + ( + cd main-repo && + c1=$(commit_with_change HEAD file-1.txt "revert-tmp") && + c2=$(commit_with_change "$c1" file-1.txt "file 1") && + c3=$(commit_with_change "$c2" file-1.txt "revert-final") && + + # c1: new root + parent root = 2 loads. c2: root matches + # HEAD (already trusted), skipped. c3: new root + parent + # already expanded = 1 load. Total: 3 trees, 2 blobs. + check_connected_trace trace-revert.txt 3 2 "$c3" + ) +' + +test_expect_success "$mode: handles subtree moved to another path" ' + ( + cd main-repo && + moved_tree=$(git ls-tree HEAD | + sed "s/ a$/ moved/" | + git mktree) && + moved=$(git commit-tree "$moved_tree" -p HEAD -m move) && + # New root + parent root scanned, but the moved subtree + # (same OID) is trusted and not descended into. + check_connected_trace trace-move.txt 2 0 "$moved" + ) +' + +test_expect_success "$mode: handles multi-parent merge" ' + ( + cd main-repo && + left=$(commit_with_change HEAD file-1.txt left) && + right=$(commit_with_change HEAD file-2.txt right) && + git update-ref refs/heads/left "$left" && + git update-ref refs/heads/right "$right" && + left_blob=$(git rev-parse "$left:file-1.txt") && + right_blob=$(git rev-parse "$right:file-2.txt") && + tmpgit read-tree HEAD && + tmpgit update-index --replace \ + --cacheinfo "100644,$left_blob,file-1.txt" && + tmpgit update-index --replace \ + --cacheinfo "100644,$right_blob,file-2.txt" && + merge_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + merge=$(git commit-tree "$merge_tree" \ + -p "$left" -p "$right" -m merge) && + # Both parent root trees are scanned as bases, so + # blobs from each parent are trusted without ODB checks. + check_connected_trace trace-merge.txt 3 0 "$merge" && + git update-ref -d refs/heads/left && + git update-ref -d refs/heads/right + ) +' + +test_expect_success "$mode: handles merge with incoming and boundary parents" ' + ( + cd main-repo && + # parent1 is incoming (not a ref), HEAD is boundary. + parent1=$(commit_with_change HEAD file-1.txt merge-inc) && + merge=$(git commit-tree \ + "$(git rev-parse "$parent1^{tree}")" \ + -p "$parent1" -p HEAD -m merge-mixed) && + # parent1 verified first (topo order): 2 trees, 1 blob. + # merge tree = parent1 tree (already trusted): 0 extra. + check_connected_trace trace-merge-inc.txt 2 1 "$merge" + ) +' + +test_expect_success "$mode: handles gitlink entries (submodules)" ' + ( + cd main-repo && + tmpgit read-tree HEAD && + tmpgit update-index --add \ + --cacheinfo "160000,$missing_oid,my-submodule" && + gitlink_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + gitlink_commit=$(git commit-tree "$gitlink_tree" -p HEAD \ + -m "add gitlink") && + + # Gitlink entries are skipped -- the missing submodule + # commit OID does not cause a failure. + check_connected_trace trace-gitlink.txt 2 0 "$gitlink_commit" + ) +' + +test_expect_success "$mode: handles file-to-directory transition" ' + ( + cd main-repo && + + # Parent: "foo" is a blob at root. + blob_a=$(echo "file-content" | git hash-object -w --stdin) && + tmpgit read-tree HEAD && + tmpgit update-index --add \ + --cacheinfo "100644,$blob_a,foo" && + parent_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + parent=$(git commit-tree "$parent_tree" -p HEAD \ + -m "add foo as file") && + + # Child: "foo" becomes a directory (foo/bar.txt). + blob_b=$(echo "dir-content" | git hash-object -w --stdin) && + tmpgit read-tree "$parent" && + tmpgit update-index --remove foo && + tmpgit update-index --add \ + --cacheinfo "100644,$blob_b,foo/bar.txt" && + child_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + child=$(git commit-tree "$child_tree" -p "$parent" \ + -m "foo: file to directory") && + check_connected_trace trace-f2d.txt "" "" "$child" + ) +' + +test_expect_success "$mode: handles directory-to-file transition" ' + ( + cd main-repo && + + # Parent: "bar/baz.txt" exists (bar is a directory). + blob_a=$(echo "nested" | git hash-object -w --stdin) && + tmpgit read-tree HEAD && + tmpgit update-index --add \ + --cacheinfo "100644,$blob_a,bar/baz.txt" && + parent_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + parent=$(git commit-tree "$parent_tree" -p HEAD \ + -m "add bar as directory") && + + # Child: "bar" becomes a plain file. + blob_b=$(echo "flat" | git hash-object -w --stdin) && + tmpgit read-tree "$parent" && + tmpgit update-index --remove bar/baz.txt && + tmpgit update-index --add \ + --cacheinfo "100644,$blob_b,bar" && + child_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + child=$(git commit-tree "$child_tree" -p "$parent" \ + -m "bar: directory to file") && + check_connected_trace trace-d2f.txt "" "" "$child" + ) +' + +# Replacement objects. + +test_expect_success "$mode: accepts with replacement objects" ' + ( + cd replace-test && + check_connected "$original_oid" + ) +' + +test_expect_success "$mode: rejects without replacement objects" ' + ( + cd replace-test && + GIT_NO_REPLACE_OBJECTS=1 && + export GIT_NO_REPLACE_OBJECTS && + test_expect_code 128 check_connected \ + "$original_oid" 2>err && + test_grep "missing blob object" err + ) +' + +test_expect_success "$mode: accepts missing promised blob" ' + test_when_finished "rm -rf prom-src prom-server.git prom-client" && + git init prom-src && + test_commit -C prom-src --no-tag base file.txt original && + test_commit -C prom-src --no-tag "add file2" file2.txt extra && + git clone --bare prom-src prom-server.git && + git -C prom-server.git config uploadpack.allowfilter true && + git -C prom-server.git config uploadpack.allowanysha1inwant true && + git clone --no-checkout --filter=blob:none \ + "file://$(pwd)/prom-server.git" prom-client && + ( + cd prom-client && + promised_blob=$(git rev-parse HEAD:file2.txt) && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_blob" && + new_tree=$(printf "100644 blob %s\tnewname.txt\n" \ + "$promised_blob" | + git mktree --missing) && + new_commit=$(git commit-tree "$new_tree" \ + -p HEAD -m "reuse promised blob") && + check_connected "$new_commit" && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_blob" + ) +' + +test_expect_success "$mode: accepts missing promised tree" ' + test_when_finished "rm -rf prom-tree-src prom-tree-server.git prom-tree-client" && + git init prom-tree-src && + mkdir -p prom-tree-src/a/b && + test_commit -C prom-tree-src --no-tag "nested dirs" a/b/file.txt deep && + git clone --bare prom-tree-src prom-tree-server.git && + git -C prom-tree-server.git config uploadpack.allowfilter true && + git -C prom-tree-server.git config uploadpack.allowanysha1inwant true && + git clone --no-checkout --filter=tree:1 \ + "file://$(pwd)/prom-tree-server.git" prom-tree-client && + ( + cd prom-tree-client && + promised_tree=$(git ls-tree HEAD -- a | + awk "{print \$3}") && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_tree" && + new_tree=$(printf "40000 tree %s\trenamed\n" \ + "$promised_tree" | + git mktree --missing) && + new_commit=$(git commit-tree "$new_tree" \ + -p HEAD -m "reuse promised tree") && + check_connected "$new_commit" && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_tree" + ) +' + +test_expect_success "$mode: verifies new subtree when parent subtree is promised" ' + test_when_finished "rm -rf prom-base-src prom-base-server.git prom-base-client" && + git init prom-base-src && + mkdir -p prom-base-src/a && + test_commit -C prom-base-src --no-tag "base" a/file.txt deep && + git clone --bare prom-base-src prom-base-server.git && + git -C prom-base-server.git config uploadpack.allowfilter true && + git -C prom-base-server.git config uploadpack.allowanysha1inwant true && + git clone --no-checkout --filter=tree:1 \ + "file://$(pwd)/prom-base-server.git" prom-base-client && + ( + cd prom-base-client && + parent_subtree=$(git ls-tree HEAD -- a | + awk "{print \$3}") && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$parent_subtree" && + new_blob=$(echo "local-content" | git hash-object -w --stdin) && + new_subtree=$(printf "100644 blob %s\tfile.txt\n" \ + "$new_blob" | git mktree) && + new_root=$(printf "40000 tree %s\ta\n" \ + "$new_subtree" | git mktree) && + new_commit=$(git commit-tree "$new_root" \ + -p HEAD -m "replace promised subtree") && + check_connected "$new_commit" && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$parent_subtree" + ) +' + +test_expect_success "$mode: verifies local commit in partial clone" ' + test_when_finished "rm -rf pc-src pc-server.git pc-client" && + git init pc-src && + test_commit -C pc-src --no-tag base file.txt && + git clone --bare pc-src pc-server.git && + git -C pc-server.git config uploadpack.allowfilter true && + git -C pc-server.git config uploadpack.allowanysha1inwant true && + git clone --filter=blob:none \ + "file://$(pwd)/pc-server.git" pc-client && + ( + cd pc-client && + local_commit=$(commit_with_change HEAD file.txt local-content) && + check_connected "$local_commit" + ) +' + +test_expect_success "$mode: respects shallow boundary" ' + test_when_finished "rm -rf shallow-src shallow" && + git init shallow-src && + test_commit -C shallow-src --no-tag base file content-1 && + mkdir shallow-src/sub && + test_commit -C shallow-src --no-tag change sub/other content-2 && + git clone --depth=1 "file://$(pwd)/shallow-src" shallow && + ( + cd shallow && + tip=$(git rev-parse HEAD) && + git for-each-ref --format="delete %(refname)" | + git update-ref --no-deref --stdin && + check_connected "$tip" + ) +' + +test_expect_success "$mode: deepening fetch succeeds" ' + test_when_finished "rm -rf deepen-src deepen-server.git deepen-client" && + git init deepen-src && + test_commit -C deepen-src --no-tag c1 file.txt && + test_commit -C deepen-src --no-tag c2 file.txt && + test_commit -C deepen-src --no-tag c3 file.txt && + git clone --bare deepen-src deepen-server.git && + git clone --depth=1 "file://$(pwd)/deepen-server.git" deepen-client && + set_connectivity_check deepen-client $mode && + test -f deepen-client/.git/shallow && + GIT_TRACE2_EVENT="$(pwd)/deepen-trace.txt" \ + git -C deepen-client fetch --deepen=2 origin main && + # Incremental falls back to full for deepening fetches, + # so the trees_loaded event should not appear. + test_grep ! trees_loaded deepen-trace.txt +' + +test_expect_success "$mode: malformed tree detected" ' + ( + cd main-repo && + echo abc >malformed-tree && + malformed_tree=$(git hash-object --literally -t tree -w \ + malformed-tree) && + malformed_commit=$(git commit-tree "$malformed_tree" \ + -p HEAD -m malformed) && + test_expect_code 128 check_connected \ + "$malformed_commit" 2>err + ) +' + +test_expect_success PERL_TEST_HELPERS \ + "$mode: mid-tree corruption detected" ' + ( + cd main-repo && + # Build a tree with one valid entry followed by garbage. + blob_oid=$(echo "valid" | git hash-object -w --stdin) && + bin_oid=$(echo "$blob_oid" | hex2oct) && + printf "100644 good\0${bin_oid}GARBAGE" >corrupt-mid-tree && + corrupt_tree=$(git hash-object --literally -t tree -w \ + corrupt-mid-tree) && + corrupt_commit=$(git commit-tree "$corrupt_tree" \ + -p HEAD -m "mid-tree corruption") && + test_expect_code 128 check_connected \ + "$corrupt_commit" 2>err && + test_grep "too-short tree object" err + ) +' + +done + +# Algorithm selection. + +test_expect_success 'invalid transfer.connectivityCheck is rejected' ' + test_when_finished "rm -rf invalid-cfg-src invalid-cfg-dst" && + git init invalid-cfg-src && + test_commit -C invalid-cfg-src --no-tag base file.txt && + git clone invalid-cfg-src invalid-cfg-dst && + test_commit -C invalid-cfg-src --no-tag update file.txt updated && + git -C invalid-cfg-dst config transfer.connectivityCheck bogus && + test_must_fail git -C invalid-cfg-dst fetch origin main 2>err && + test_grep "unknown transfer.connectivityCheck" err +' + +test_expect_success 'push uses incremental when configured' ' + test_when_finished "rm -rf int-src int-dst.git" && + git init int-src && + test_commit -C int-src --no-tag base file.txt && + git clone --bare int-src int-dst.git && + test_commit -C int-src --no-tag update file.txt updated && + set_connectivity_check int-dst.git incremental && + GIT_TRACE2_EVENT="$(pwd)/push-trace.txt" \ + git -C int-src push ../int-dst.git main && + test_trace2_data_singular connectivity trees_loaded 2 \ + kh_val(m, pos)) + kh_val(m, pos) = state; +} + +struct work_item { + struct name_entry entry; + struct oid_array parent_trees; +}; + +struct verify_state { + kh_oid_tree_t *trees; + struct oidset trusted_blobs; + int trees_loaded; + int blobs_checked; + int exclude_promisor_objects; +}; + +/* + * Merge-walk the work list against one base tree entry, recording + * same-path parent subtrees as recursive comparison bases. + * Returns the updated work-list cursor. + */ +static size_t collect_subtree_bases(struct work_item *work, size_t nr_work, + size_t wi, const struct name_entry *entry) +{ + while (wi < nr_work) { + int cmp = base_name_compare( + work[wi].entry.path, work[wi].entry.pathlen, + work[wi].entry.mode, + entry->path, entry->pathlen, + entry->mode); + if (cmp > 0) + break; + if (cmp < 0) { + wi++; + continue; + } + if (S_ISDIR(work[wi].entry.mode) && + S_ISDIR(entry->mode)) + oid_array_append(&work[wi].parent_trees, + &entry->oid); + return wi + 1; + } + return wi; +} + +static void verify_blob(struct repository *repo, + const struct object_id *oid, + struct verify_state *vs) +{ + int type; + + if (oidset_contains(&vs->trusted_blobs, oid)) + return; + + vs->blobs_checked++; + type = odb_read_object_info(repo->objects, oid, NULL); + if (type == OBJ_BLOB) { + oidset_insert(&vs->trusted_blobs, oid); + return; + } + if (type >= 0) + die(_("object %s is a %s, not a blob"), + oid_to_hex(oid), type_name(type)); + if (vs->exclude_promisor_objects && + is_promisor_object(repo, oid)) + return; + die(_("missing blob object '%s'"), oid_to_hex(oid)); +} + +static void *read_tree_object(struct object_database *odb, + const struct object_id *oid, + size_t *sizep) +{ + enum object_type type; + void *buf = odb_read_object(odb, oid, &type, sizep); + + if (buf && type != OBJ_TREE) { + free(buf); + die(_("object %s is a %s, not a tree"), + oid_to_hex(oid), type_name(type)); + } + return buf; +} + +static void verify_tree(struct repository *repo, + const struct object_id *new_tree_oid, + const struct oid_array *base_trees, + struct verify_state *vs, int depth) +{ + struct tree_desc desc; + struct name_entry entry; + struct work_item *work = NULL; + size_t nr_work = 0, alloc_work = 0; + int need_subtree_bases = 0; + size_t i, tree_size; + void *tree_buf; + + if (depth > repo->settings.max_allowed_tree_depth) + die(_("exceeded maximum allowed tree depth")); + + if (tree_map_get(vs->trees, new_tree_oid) >= TREE_TRUSTED) + return; + + tree_buf = read_tree_object(repo->objects, new_tree_oid, &tree_size); + if (!tree_buf) { + if (vs->exclude_promisor_objects && + is_promisor_object(repo, new_tree_oid)) + return; + die(_("bad tree object %s"), + oid_to_hex(new_tree_oid)); + } + + vs->trees_loaded++; + init_tree_desc(&desc, new_tree_oid, tree_buf, tree_size); + + while (tree_entry(&desc, &entry)) { + if (S_ISGITLINK(entry.mode)) + continue; + if (S_ISDIR(entry.mode)) { + if (tree_map_get(vs->trees, &entry.oid) >= TREE_TRUSTED) + continue; + need_subtree_bases = 1; + } else { + if (oidset_contains(&vs->trusted_blobs, &entry.oid)) + continue; + } + ALLOC_GROW(work, nr_work + 1, alloc_work); + memset(&work[nr_work], 0, sizeof(work[nr_work])); + work[nr_work].entry = entry; + nr_work++; + } + + if (!nr_work) { + free(tree_buf); + goto done; + } + + for (i = 0; base_trees && i < base_trees->nr; i++) { + const struct object_id *base_oid = &base_trees->oid[i]; + int expanded = tree_map_get(vs->trees, base_oid) >= TREE_EXPANDED; + struct tree_desc base_desc; + struct name_entry scan_entry; + size_t wi = 0, base_size; + void *base_buf; + + if (expanded && !need_subtree_bases) + continue; + + base_buf = read_tree_object(repo->objects, base_oid, + &base_size); + if (!base_buf) { + if (vs->exclude_promisor_objects && + is_promisor_object(repo, base_oid)) + continue; + die(_("bad tree object %s"), + oid_to_hex(base_oid)); + } + + vs->trees_loaded++; + init_tree_desc(&base_desc, base_oid, base_buf, base_size); + + while (tree_entry(&base_desc, &scan_entry)) { + if (S_ISGITLINK(scan_entry.mode)) + continue; + + if (need_subtree_bases) + wi = collect_subtree_bases(work, nr_work, + wi, &scan_entry); + + if (!expanded) { + if (S_ISDIR(scan_entry.mode)) + tree_map_add(vs->trees, + &scan_entry.oid, + TREE_TRUSTED); + else + oidset_insert(&vs->trusted_blobs, + &scan_entry.oid); + } + } + + if (!expanded) + tree_map_add(vs->trees, base_oid, TREE_EXPANDED); + + free(base_buf); + } + + for (i = 0; i < nr_work; i++) { + if (S_ISDIR(work[i].entry.mode)) + verify_tree(repo, &work[i].entry.oid, + &work[i].parent_trees, vs, + depth + 1); + else + verify_blob(repo, &work[i].entry.oid, vs); + } + + free(tree_buf); + +done: + tree_map_add(vs->trees, new_tree_oid, TREE_EXPANDED); + for (i = 0; i < nr_work; i++) + oid_array_clear(&work[i].parent_trees); + free(work); +} + +static void verify_commit_tree(struct repository *repo, + struct commit *commit, + struct verify_state *vs) +{ + struct oid_array base_trees = OID_ARRAY_INIT; + struct commit_list *p; + + /* + * Parent trees are trusted: boundary parents are already + * connected, and earlier incoming parents were verified + * first due to the topological processing order. + */ + for (p = commit->parents; p; p = p->next) { + const struct object_id *tree_oid; + parse_commit_or_die(p->item); + tree_oid = get_commit_tree_oid(p->item); + tree_map_add(vs->trees, tree_oid, TREE_TRUSTED); + oid_array_append(&base_trees, tree_oid); + } + + verify_tree(repo, get_commit_tree_oid(commit), + &base_trees, vs, 0); + oid_array_clear(&base_trees); +} + +void verify_commits_incremental(struct repository *repo, + struct commit_list **commits, + int exclude_promisor_objects) +{ + struct verify_state vs = { 0 }; + struct commit_list *iter; + unsigned nr_before; + + vs.trees = kh_init_oid_tree(); + vs.exclude_promisor_objects = exclude_promisor_objects; + + /* + * Ancestors must be verified before descendants so that parent + * trees can be trusted without re-verification. Sort explicitly + * rather than relying on the caller's ordering. + * + * sort_in_topological_order() silently drops cycle members, + * so explicitly check if the size has changed. + */ + nr_before = commit_list_count(*commits); + sort_in_topological_order(commits, REV_SORT_IN_GRAPH_ORDER); + if (commit_list_count(*commits) < nr_before) + die(_("cycle detected in incoming commit graph")); + + *commits = commit_list_reverse(*commits); + + for (iter = *commits; iter; iter = iter->next) + verify_commit_tree(repo, iter->item, &vs); + + kh_destroy_oid_tree(vs.trees); + oidset_clear(&vs.trusted_blobs); + trace2_data_intmax("connectivity", repo, + "trees_loaded", vs.trees_loaded); + trace2_data_intmax("connectivity", repo, + "blobs_checked", vs.blobs_checked); +} diff --git a/tree-verify.h b/tree-verify.h new file mode 100644 index 0000000000..6aadadff70 --- /dev/null +++ b/tree-verify.h @@ -0,0 +1,15 @@ +#ifndef TREE_VERIFY_H +#define TREE_VERIFY_H + +struct commit_list; +struct repository; + +/* + * Verify trees of commits incrementally against their parents. + * Dies on verification failure. + */ +void verify_commits_incremental(struct repository *repo, + struct commit_list **commits, + int exclude_promisor_objects); + +#endif /* TREE_VERIFY_H */ -- gitgitgadget ``` ## Junio C Hamano, 2026-09-14 15:12 Subject: Re: [PATCH 0/2] connected: add incremental connectivity check Message-ID: In-Reply-To: ``` "Kristofer Karlsson via GitGitGadget" writes: > This series adds an incremental mode for the connectivity check, gated > behind transfer.connectivityCheck=incremental (no expected changes unless > you opt in). > > The intent is to solve the problem of the connectivity check slowing down as > the number of reachable objects from the boundary grows. Exciting benchmarks. ``` ## Junio C Hamano, 2026-09-14 15:26 Subject: Re: [PATCH 2/2] connected: add incremental connectivity check via rev-list Message-ID: In-Reply-To: ``` "Kristofer Karlsson via GitGitGadget" writes: > +static void verify_blob(struct repository *repo, > + const struct object_id *oid, > + struct verify_state *vs) > +{ > + int type; > + > + if (oidset_contains(&vs->trusted_blobs, oid)) > + return; > + > + vs->blobs_checked++; > + type = odb_read_object_info(repo->objects, oid, NULL); > + if (type == OBJ_BLOB) { > + oidset_insert(&vs->trusted_blobs, oid); > + return; > + } > + if (type >= 0) > + die(_("object %s is a %s, not a blob"), > + oid_to_hex(oid), type_name(type)); > + if (vs->exclude_promisor_objects && > + is_promisor_object(repo, oid)) > + return; > + die(_("missing blob object '%s'"), oid_to_hex(oid)); > +} I wonder if this is_promisor_object() call comes a bit too late, as we earlier already have called odb_read_object_info() which may have fetched it lazily from the promisor remote? Or do we globally disable promisor_remote_get_direct() call somehow without having to pass OBJECT_INFO_SKIP_FETCH_OBJECT flag? > +static void verify_commit_tree(struct repository *repo, > + struct commit *commit, > + struct verify_state *vs) > +{ > + struct oid_array base_trees = OID_ARRAY_INIT; > + struct commit_list *p; > + > + /* > + * Parent trees are trusted: boundary parents are already > + * connected, and earlier incoming parents were verified > + * first due to the topological processing order. > + */ > + for (p = commit->parents; p; p = p->next) { > + const struct object_id *tree_oid; > + parse_commit_or_die(p->item); > + tree_oid = get_commit_tree_oid(p->item); > + tree_map_add(vs->trees, tree_oid, TREE_TRUSTED); > + oid_array_append(&base_trees, tree_oid); > + } > + > + verify_tree(repo, get_commit_tree_oid(commit), > + &base_trees, vs, 0); > + oid_array_clear(&base_trees); > +} Do we assume that we do not have to deal with repository corruption in any graceful way? I am just wondering what happens when get_commit_tree_oid() yields NULL after parse_commit_or_die() finds p->item is a valid-looking commit object but the tree within it is not, and we end up passing NULL to tree_map_add(), perhaps? The same potential issue may exist in the get_commit_tree_oid() call outside the look at the end on the incoming commit's tree. ``` ## Kristofer Karlsson, 2026-09-14 17:46 Subject: Re: [PATCH 2/2] connected: add incremental connectivity check via rev-list Message-ID: In-Reply-To: ``` On Mon, 14 Sept 2026 at 17:26, Junio C Hamano wrote: > > "Kristofer Karlsson via GitGitGadget" > writes: > > I wonder if this is_promisor_object() call comes a bit too late, as > we earlier already have called odb_read_object_info() which may have > fetched it lazily from the promisor remote? Or do we globally > disable promisor_remote_get_direct() call somehow without having to > pass OBJECT_INFO_SKIP_FETCH_OBJECT flag? Yes, I think it's safe due to the following mechanism: 1. If promisors exist, the connectivity-check will invoke rev-list with --exclude-promisor-objects. 2. rev-list in turn sets repo->fetch_if_missing = 0 on startup. 3. Then the odb read goes down into do_oid_object_info_extended() which respects that flag. However, my paranoia kicked in so I re-ran my test for this, after adding some temporary code inside verify_commits_incremental(): repo->fetch_if_missing = 1; And fortunately, one of the tests failed as expected. Exactly 1 failure out of 62 tests: test 53 "incremental: verifies new subtree when parent subtree is promised". And the relevant assertion is this one: test_must_fail env GIT_NO_LAZY_FETCH=1 \ git cat-file -e "$parent_subtree" which ensures that the object was never fetched. However, the test only catches this scenario for trees, not blobs -- that's an oversight, I will add a matching test for blobs too. I think the code technically works as-is, but I could also try to rewrite the code to stop depending on odb_read_object_info() and instead use odb_read_object_info_extended() which allows me to pass the flags. That gives us belts and suspenders, which may be nicer here. > Do we assume that we do not have to deal with repository corruption > in any graceful way? I am just wondering what happens when > get_commit_tree_oid() yields NULL after parse_commit_or_die() finds > p->item is a valid-looking commit object but the tree within it is > not, and we end up passing NULL to tree_map_add(), perhaps? > > The same potential issue may exist in the get_commit_tree_oid() call > outside the look at the end on the incoming commit's tree. You're right, this is an oversight. I think I incorrectly assumed that parse_commit_or_die() would catch any malformed commit. I will add a NULL check and a die()-exit at the two call sites in verify_commit_tree() die(_("unable to load root tree for commit %s"), oid_to_hex(&commit->object.oid)); Thanks for spotting these errors, Kristofer ``` ## Kristofer Karlsson via GitGitGadget, 2026-09-28 13:02 Subject: [PATCH v2 0/2] connected: add incremental connectivity check Message-ID: In-Reply-To: ``` This series adds an incremental mode for the connectivity check, gated behind transfer.connectivityCheck=incremental (no expected changes unless you opt in). The intent is to solve the problem of the connectivity check slowing down as the number of reachable objects from the boundary grows. It relates to the RFC I sent out earlier: [RFC] check_connected: toward incoming-proportional cost https://lore.kernel.org/git/CAL71e4Nf=-zCrfN7ghEVGq11irajJhtdxYZgKe0Ycux0qs1ZvQ@mail.gmail.com/ Design ====== The verifier runs inside the same rev-list subprocess that check_connected() already spawns, triggered by a new internal flag --verify-trees-incremental. After get_revision() collects the incoming commits, the verifier processes them in topological order (ancestors before descendants). The idea is to keep a set of trusted objects, shared across the incoming commits, that grows over time. We visit the new/untrusted commit trees and do a comparison walk over the trees of their parents. Entries discovered on the trusted parent side are remembered as trusted, which lets later verification skip matching objects and avoid descending into unchanged subtrees. More algorithmic details are in Documentation/technical/connectivity-check.adoc. Benchmarks ========== I'll just mention a short summary here, to avoid repeating what's already in the commit message. The incremental mode is faster than the full mode when there are few commits to verify and when the active object tree is large. In the happy case, the work tracks the changed paths and their comparison trees rather than the full reachable object closure, which substantially reduces the dependence on total repository size. I've seen speedups up to around 20x for the synthetic perf tests. Running against a large real-world repo (3.4 GB boundary closure), the numbers are more dramatic. All timings use rev-list directly with --not HEADN, isolating the tree verification cost from the boundary-finding cost: commits full incr. speedup full RSS incr. RSS 1 1.9s 0.01s 190x 3.4 GB 14 MB 10 1.9s 0.04s 48x 3.4 GB 125 MB 100 1.9s 0.37s 5x 3.4 GB 1.1 GB The full mode takes ~1.9s regardless of commit count because it is dominated by walking the boundary closure. Incremental scales with the number of incoming commits and the paths they touch. Memory follows the same pattern: incremental uses a fraction of the full mode's RSS for small pushes, converging only when many commits are verified. There are also regression cases in the synthetic fixtures. With long incoming histories, the extra parent-tree scans accumulate; in the synthetic fixture incremental is about 1.5x slower at 10000 commits. Per-commit changes have less impact than expected: even when every directory is touched, incremental remains competitive; bypassing the object cache for tree reads likely helps here. I cannot establish how common these regression cases are. In the cases I have tested, however, the regression has remained modest; I have not been able to provoke a substantially larger slowdown. My feeling is that this is an acceptable tradeoff behind the opt-in config, since the target case (small pushes to large repos) sees the largest speedup, while the regression appears with long incoming histories. A safety net for this regression could be to dynamically disable the incremental mode if the number of incoming commits is too large, but this is left out of the initial version to avoid overly speculative code. Deepening fetches currently fall back to the full check because the full check omits --not --all for deepening -- there is no existing-reference boundary at which the walk can stop. An incremental approach is possible here too -- using the old shallow roots as the trusted boundary and walking the deepened ancestry forward -- but that is a separate change and left for future work. Deepening is also less common than regular fetch and receive-pack, where the speedup matters most. Test coverage ============= Most correctness cases in t5412-connectivity-check.sh are run in both full and incremental modes to check semantic equivalence. Selected cases additionally assert trace2 tree/blob counts for the incremental mode, to verify that unchanged portions of the object graph are actually skipped. It covers: * Corruption detection: missing blobs, missing trees, type mismatches, malformed trees (unparseable, mid-tree corruption) * Tree optimization: trace2 assertions confirm unchanged subtrees are skipped, subtree moves, merge parent boundaries * Root commits (no parents -- verifies full tree closure) * Partial clones: missing promised blobs, missing promised trees, verification of local commits * Replacement objects (with and without GIT_NO_REPLACE_OBJECTS) * Shallow boundaries * Deepening fetches (falls back to full check) * Integration: real push, fetch, and clone Most tests call git rev-list directly with the appropriate flags; integration tests exercise the full check_connected() path through push, fetch, and clone. Alternatives considered ======================= My first prototype ran the verifier in-process inside connected.c. This required a second rev-list subprocess just for boundary finding, _nofetch variants of several object-reading functions to prevent lazy fetches in partial clones, explicit shallow-file plumbing, and careful avoidance of die() in all code paths reachable from the verifier. The result worked but was fragile and touched many files. Moving the verifier into the rev-list subprocess eliminated all of those problems: in partial clones the existing --exclude-promisor-objects handling already disables lazy fetching, die() is isolated by the process boundary, shallow and replacement semantics are established before the verifier runs, and error routing comes for free via stderr. So while I liked the idea of being less reliant on checking within a subprocess, making that work ended up being a lot more complex. Next steps ========== This series only addresses tree verification; the other significant cost is finding the commit boundary, especially for repos with many refs. I already have some prototypes for optimizing that too, and if this ends up landing, that would be something I would start polishing up. Changes since v1 ================ * Guard against get_commit_tree_oid() returning NULL in verify_commit_tree(), dying with a clear message instead of a NULL dereference. (Thanks Junio for catching this) * Set fetch_if_missing = 0 in the rev-list early option parse when --verify-trees-incremental is seen, and add a BUG() assertion in verify_commits_incremental() to catch any future caller that forgets. This makes the lazy-fetch protection explicit rather than relying solely on --exclude-promisor-objects having set it earlier. (Thanks again to Junio) * Add a test that verifies promised blobs are not lazy-fetched during the incremental check. * Reuse the existing 3-argument type-mismatch format string to avoid adding new strings for localization. Thanks, Kristofer Kristofer Karlsson (2): Documentation: describe connectivity checking connected: add incremental connectivity check via rev-list Documentation/config/transfer.adoc | 20 + Documentation/rev-list-options.adoc | 6 + .../technical/connectivity-check.adoc | 243 +++++++ Makefile | 1 + builtin/rev-list.c | 19 + connected.c | 24 + meson.build | 1 + t/meson.build | 1 + ...enerate-repo-p5412-connectivity-check.perl | 44 ++ t/perf/p5412-connectivity-check.sh | 92 +++ t/t5412-connectivity-check.sh | 680 ++++++++++++++++++ tree-verify.c | 316 ++++++++ tree-verify.h | 15 + 13 files changed, 1462 insertions(+) create mode 100644 Documentation/technical/connectivity-check.adoc create mode 100644 t/perf/generate-repo-p5412-connectivity-check.perl create mode 100755 t/perf/p5412-connectivity-check.sh create mode 100755 t/t5412-connectivity-check.sh create mode 100644 tree-verify.c create mode 100644 tree-verify.h base-commit: 47ce80527c56f462cb97db4ca8125342204d3783 Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2211%2Fspkrka%2Ftree-diff-connectivity-v1-clean-v2 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2211/spkrka/tree-diff-connectivity-v1-clean-v2 Pull-Request: https://github.com/gitgitgadget/git/pull/2211 Range-diff vs v1: 1: e55c5452db = 1: 97c11449ae Documentation: describe connectivity checking 2: ebe6c90cc5 ! 2: 6ad528f4bb connected: add incremental connectivity check via rev-list @@ builtin/rev-list.c: int cmd_rev_list(int argc, revs.exclude_promisor_objects = 1; + } else if (!strcmp(arg, "--verify-trees-incremental")) { + verify_trees_incremental = 1; ++ repo->fetch_if_missing = 0; } else if (skip_prefix(arg, "--missing=", &arg)) { parse_missing_action_value(repo, arg); } else if (!strcmp(arg, "-z")) { @@ t/t5412-connectivity-check.sh (new) + ) +' + ++test_expect_success "$mode: does not lazy-fetch promised blob" ' ++ test_when_finished "rm -rf nofetch-src nofetch-server.git nofetch-client" && ++ git init nofetch-src && ++ test_commit -C nofetch-src --no-tag base file.txt content && ++ git clone --bare nofetch-src nofetch-server.git && ++ git -C nofetch-server.git config uploadpack.allowfilter true && ++ git -C nofetch-server.git config uploadpack.allowanysha1inwant true && ++ git clone --no-checkout --filter=blob:none \ ++ "file://$(pwd)/nofetch-server.git" nofetch-client && ++ ( ++ cd nofetch-client && ++ promised_blob=$(git rev-parse HEAD:file.txt) && ++ test_must_fail env GIT_NO_LAZY_FETCH=1 \ ++ git cat-file -e "$promised_blob" && ++ new_tree=$(printf "100644 blob %s\tfile.txt\n" \ ++ "$promised_blob" | ++ git mktree --missing) && ++ new_commit=$(git commit-tree "$new_tree" \ ++ -m "root commit with promised blob") && ++ check_connected "$new_commit" && ++ test_must_fail env GIT_NO_LAZY_FETCH=1 \ ++ git cat-file -e "$promised_blob" ++ ) ++' ++ +test_expect_success "$mode: accepts missing promised tree" ' + test_when_finished "rm -rf prom-tree-src prom-tree-server.git prom-tree-client" && + git init prom-tree-src && @@ tree-verify.c (new) + return; + } + if (type >= 0) -+ die(_("object %s is a %s, not a blob"), -+ oid_to_hex(oid), type_name(type)); ++ die(_("object %s is a %s, not a %s"), ++ oid_to_hex(oid), type_name(type), "blob"); + if (vs->exclude_promisor_objects && + is_promisor_object(repo, oid)) + return; @@ tree-verify.c (new) + + if (buf && type != OBJ_TREE) { + free(buf); -+ die(_("object %s is a %s, not a tree"), -+ oid_to_hex(oid), type_name(type)); ++ die(_("object %s is a %s, not a %s"), ++ oid_to_hex(oid), type_name(type), "tree"); + } + return buf; +} @@ tree-verify.c (new) + const struct object_id *tree_oid; + parse_commit_or_die(p->item); + tree_oid = get_commit_tree_oid(p->item); ++ if (!tree_oid) ++ die(_("unable to load root tree for commit %s"), ++ oid_to_hex(&p->item->object.oid)); + tree_map_add(vs->trees, tree_oid, TREE_TRUSTED); + oid_array_append(&base_trees, tree_oid); + } + ++ if (!get_commit_tree_oid(commit)) ++ die(_("unable to load root tree for commit %s"), ++ oid_to_hex(&commit->object.oid)); + verify_tree(repo, get_commit_tree_oid(commit), + &base_trees, vs, 0); + oid_array_clear(&base_trees); @@ tree-verify.c (new) + struct commit_list *iter; + unsigned nr_before; + ++ if (repo->fetch_if_missing) ++ BUG("verify_commits_incremental must not be called " ++ "with fetch_if_missing set"); ++ + vs.trees = kh_init_oid_tree(); + vs.exclude_promisor_objects = exclude_promisor_objects; + -- gitgitgadget ``` ## Kristofer Karlsson via GitGitGadget, 2026-09-28 13:02 Subject: [PATCH v2 1/2] Documentation: describe connectivity checking Message-ID: <97c11449aeae924436ba22a00a2545254e988a58.1790600552.git.gitgitgadget@gmail.com> In-Reply-To: ``` From: Kristofer Karlsson Add Documentation/technical/connectivity-check.adoc describing the connectivity invariant and the full connectivity check. Signed-off-by: Kristofer Karlsson --- .../technical/connectivity-check.adoc | 109 ++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 Documentation/technical/connectivity-check.adoc diff --git a/Documentation/technical/connectivity-check.adoc b/Documentation/technical/connectivity-check.adoc new file mode 100644 index 0000000000..d20bff6af6 --- /dev/null +++ b/Documentation/technical/connectivity-check.adoc @@ -0,0 +1,109 @@ +Connectivity checking +===================== + +After receiving new objects via fetch, push (receive-pack), clone, +or bundle, Git verifies that the new reference tips do not leave +the repository in a state where reachable objects are missing. +This verification is called the connectivity check. + +Connectivity invariant +---------------------- + +A repository is connected when every object reachable from its +references is available locally (with exceptions noted below). + +The connectivity check maintains this invariant when references +are updated. It trusts the existing connected state and verifies +that the new reference tips do not introduce references to +unavailable objects. Verification is permitted to stop when it +reaches objects already reachable from trusted existing +references, since their closure is already connected. These +trusted references include local references and references from +alternate object stores. + +Without this check, a truncated or corrupted transfer could leave +a repository in a state where later history walks encounter +missing objects. + +Exceptions +~~~~~~~~~~ + +Gitlink entries (submodule references) are excluded from +connectivity checking. Their target objects belong to a separate +repository. + +In partial clones, objects promised by a promisor remote are +accepted as connected without requiring local existence. The +check excludes promisor objects from traversal so that it does +not trigger on-demand fetches for them. + +Full connectivity check +----------------------- + +`check_connected()` (see `connected.c`) normally performs the +connectivity check using a `rev-list` subprocess, feeding the +new reference tips via stdin. A normal invocation is roughly: + + git rev-list --objects --stdin --not --all --quiet + --alternate-refs [--exclude-promisor-objects] + +When promisor remotes are configured, `check_connected()` first +attempts a fast path based on promisor packfiles. If it falls +back to the `rev-list` check, `--exclude-promisor-objects` is +added so that the traversal does not trigger on-demand fetches. + +Consider the following graph after a fetch, where all reference +tips point directly to commits. For simplicity, only local +references appear on the already-connected side; alternate refs +play the same role. N3 is a merge commit: + + /-------------L2 + / + C1---B1---C2---B2-----L1 + \ \ + N1 N3---T2 + \ / + N2-----------T1 + + L1, L2: local refs + T1, T2: incoming tips (new refs) + N1, N2, N3: incoming commits (N3 is a merge) + B1, B2: boundary commits (already connected) + C1, C2: already connected (but not boundary) + +The incoming set is the commits reachable from the incoming +tips but not from the already-connected side. Boundary commits +are the already-connected commits at the edge of that set. Here +B1 is an ancestor of B2, which happens when incoming branches +fork at different depths in the existing history. + +The check proceeds in three phases: + +1. Walk from the incoming tips (T1, T2) against the trusted + refs (L1, L2) to find the incoming set ({N1, N2, N3, T1, T2}). + +2. Walk the trees of the boundary commits (B1, B2) and mark + those objects uninteresting. These trees are already trusted + because their commits are on the already-connected side. + +3. Walk the trees of each incoming commit and verify that every + referenced object is connected, stopping at objects already + marked uninteresting in phase 2. + +Deepening fetches +~~~~~~~~~~~~~~~~~ + +For deepening fetches (where the shallow boundary moves), the +full check omits `--not --all`. There is no existing-reference +boundary at which the walk can stop. Instead, traversal follows +the effective shallow boundary supplied for the deepened +repository. The new content may be below the old shallow +boundary even when the tips themselves have not changed. + +Non-commit tips +~~~~~~~~~~~~~~~ + +When a new reference points to a non-commit object, such as a +tag, tree, or blob, that object is not part of the commit walk. +These non-commit tips are handled by the subsequent object +traversal. -- gitgitgadget ``` ## Kristofer Karlsson via GitGitGadget, 2026-09-28 13:02 Subject: [PATCH v2 2/2] connected: add incremental connectivity check via rev-list Message-ID: <6ad528f4bb42a960910eb4fe917a3766fa55d598.1790600552.git.gitgitgadget@gmail.com> In-Reply-To: ``` From: Kristofer Karlsson The full connectivity check uses rev-list to find commits reachable from the incoming tips but not from the already-connected side, then walks their object closure. Commit traversal stops at the connectivity boundary, but trees and blobs reachable from that boundary still need to be walked so they can be marked uninteresting, allocating a struct object for each one. On repositories where the boundary commits have large trees, the connectivity check for small incoming changes visits and tracks more objects than needed. Add an alternative connectivity check that verifies incoming commits incrementally against their parents. The verifier processes incoming commits with ancestors first and compares each new tree against its trusted parent trees. Entries already seen on the trusted side are skipped by OID, so unchanged subtrees need not remain at the same path to be recognized. Changed subtrees are recursively compared against same-path parent subtrees, and new subtrees without a comparison base are verified from scratch. See Documentation/technical/connectivity-check.adoc for the trust invariants and detailed algorithm. The incremental check runs as an internal --verify-trees-incremental mode in rev-list. After the normal revision walk identifies the incoming commits, the verifier consumes them before the usual object traversal; any pending non-commit tips are still handled by the existing traversal. Partial-clone semantics are preserved: objects promised by a promisor remote are accepted as connected, and on-demand fetching is prevented by excluding promisor objects from traversal. The new mode is selected by transfer.connectivityCheck=incremental, with full remaining the default. Deepening fetches fall back to the full check because they do not have the normal existing-reference boundary, and traversal instead follows the effective shallow boundary. p5412 results (median of 3), scaling one dimension at a time. Each fixture is a repository with a flat tree of many directories containing 100 files each. The incoming set is a chain of commits on top of the existing history, with each commit changing files in different directories round-robin. The three axes vary the total repository tree size, the number of incoming commits, and the number of files changed per incoming commit. Scaling tree size (10 incoming commits, 10 files/commit): files full incr. full/incr 5K 0.01s 0.01s 1.0x 50K 0.04s 0.01s 4.0x 200K 0.15s 0.01s 15.0x 800K 0.61s 0.03s 20.3x The full mode must walk the trees of boundary commits, which grows with overall tree size. Incremental still scans the root trees, but avoids descending into unchanged subtrees, so it grows much more slowly with repository size. Scaling incoming commit count (200K files, 10 files/commit): commits full incr. full/incr 1 0.14s 0.01s 14.0x 10 0.15s 0.01s 15.0x 100 0.19s 0.05s 3.8x 500 0.32s 0.27s 1.2x 3000 1.23s 1.52s 0.8x 5000 1.88s 2.43s 0.8x 10000 3.72s 5.36s 0.7x With many commits the per-commit overhead of scanning both the new and parent root trees accumulates and incremental becomes slower. Breakeven is between 500 and 3000 commits and the ratio stabilizes near 0.7x for this fixture. Scaling files per incoming commit (200K files, 10 commits): files/commit full incr. full/incr 1 0.14s 0.01s 14.0x 10 0.15s 0.01s 15.0x 100 0.16s 0.04s 4.0x 500 0.23s 0.14s 1.6x 1000 0.34s 0.28s 1.2x 2000 0.70s 0.63s 1.1x Breakeven is around 1000 files/commit. At 2000 files/commit (every directory touched), incremental remains slightly faster; bypassing the object cache for tree reads likely helps here. For small repositories both modes are fast enough that the difference is difficult to measure reliably. Selected peak RSS measurements from the same fixtures: case full incr. ratio 200K files, 10 commits 31 MB 12 MB 0.4x 800K files, 10 commits 110 MB 26 MB 0.2x 200K files, 5000 commits 155 MB 151 MB 1.0x Incremental uses substantially less memory when it can prune most of the boundary tree walk. In the long-history case the two modes visit similar object sets and memory converges. The regression cases in the CPU benchmarks are in wall-clock time rather than memory, primarily from scanning some trees more than once. Signed-off-by: Kristofer Karlsson --- Documentation/config/transfer.adoc | 20 + Documentation/rev-list-options.adoc | 6 + .../technical/connectivity-check.adoc | 134 ++++ Makefile | 1 + builtin/rev-list.c | 19 + connected.c | 24 + meson.build | 1 + t/meson.build | 1 + ...enerate-repo-p5412-connectivity-check.perl | 44 ++ t/perf/p5412-connectivity-check.sh | 92 +++ t/t5412-connectivity-check.sh | 680 ++++++++++++++++++ tree-verify.c | 316 ++++++++ tree-verify.h | 15 + 13 files changed, 1353 insertions(+) create mode 100644 t/perf/generate-repo-p5412-connectivity-check.perl create mode 100755 t/perf/p5412-connectivity-check.sh create mode 100755 t/t5412-connectivity-check.sh create mode 100644 tree-verify.c create mode 100644 tree-verify.h diff --git a/Documentation/config/transfer.adoc b/Documentation/config/transfer.adoc index f1ce50f4a6..b9939d3bde 100644 --- a/Documentation/config/transfer.adoc +++ b/Documentation/config/transfer.adoc @@ -1,3 +1,23 @@ +transfer.connectivityCheck:: + Choose which algorithm to use for the connectivity check + performed during object transfer operations such as + linkgit:git-fetch[1] and linkgit:git-receive-pack[1]. + The connectivity check verifies that all objects reachable + from the incoming tips are available locally or, in a partial + clone, promised by a promisor remote. + The variants are as follows: ++ +-- +`full` (default);; + Walk the full object closure of the boundary commits. +`incremental`;; + Verify incoming commits by diffing their trees against parent + trees, recursively descending only into entries that differ. + The largest benefits occur when incoming commits change a + small fraction of a large tree closure. + Falls back to `full` for deepening fetches. +-- + transfer.credentialsInUrl:: A configured URL can contain plaintext credentials in the form `://:@/`. You may want diff --git a/Documentation/rev-list-options.adoc b/Documentation/rev-list-options.adoc index fd831f0ec6..7964b691c4 100644 --- a/Documentation/rev-list-options.adoc +++ b/Documentation/rev-list-options.adoc @@ -1089,6 +1089,12 @@ we cannot get their Object ID though, an error will be raised. stronger than `--missing=allow-promisor` because it limits the traversal, rather than just silencing errors about missing objects. + +`--verify-trees-incremental`:: + (For internal use only.) Verify tree connectivity + incrementally by comparing each commit's tree against its + parent trees. Used by `check_connected()` when + `transfer.connectivityCheck` is set to `incremental`. endif::git-rev-list[] `--no-walk[=(sorted|unsorted)]`:: diff --git a/Documentation/technical/connectivity-check.adoc b/Documentation/technical/connectivity-check.adoc index d20bff6af6..0a8f370546 100644 --- a/Documentation/technical/connectivity-check.adoc +++ b/Documentation/technical/connectivity-check.adoc @@ -107,3 +107,137 @@ When a new reference points to a non-commit object, such as a tag, tree, or blob, that object is not part of the commit walk. These non-commit tips are handled by the subsequent object traversal. + +Incremental connectivity check +------------------------------ + +The incremental mode, selected by +`transfer.connectivityCheck=incremental`, avoids traversing the +full tree walk of the boundary commits. Instead, it verifies +each incoming commit's tree against the already-trusted trees of +its parents. + +Trust model +~~~~~~~~~~~ + +A tree is trusted when its transitive object closure is known to +be connected. Trees reachable from commits on the +already-connected side of the boundary are therefore trusted. + +Incoming commits are processed with ancestors before descendants. +Once an incoming commit's tree has been verified, it is trusted +and can be used as a comparison base for later descendants. + +This gives an inductive correctness argument: every parent of the +commit currently being verified is either already connected or is +an earlier incoming commit whose tree has already been verified. + +Tree states +~~~~~~~~~~~ + +The verifier tracks tree OIDs in three states: + +untrusted:: + The tree has not yet been established as connected. This + is the implicit state of an OID not present in the state + map. + +trusted:: + The tree is known to have a connected transitive closure, + but its direct entries have not yet been published into the + verifier's trusted object sets. + +expanded:: + The tree is trusted and its direct non-gitlink entries + have also been published into the trusted object sets. + +State transitions are monotonic: a tree may move from untrusted +to trusted to expanded, but never backwards. An untrusted tree +that is successfully verified goes directly to expanded. + +Blobs require only trusted/untrusted state: a blob becomes +trusted when it is found in a trusted tree or when its existence +and type have been verified directly. + +The trusted/expanded distinction is an optimization. An expanded +parent does not need to be reread merely to publish entries that +are already trusted, though it may still be read when same-path +subtree bases are needed for recursive comparison. + +Algorithm +~~~~~~~~~ + +At a high level: + + verify(commits): + sort topologically (ancestors first) + for each commit: + mark parent root trees as trusted + verify_tree(commit.tree, parent root trees) + + verify_tree(tree, base_trees): + if tree already trusted: return + read tree, collect entries not already trusted + for each available base tree: + publish its entries as trusted + record same-path subtrees as bases + for each collected entry: + if now trusted: skip + if blob: verify blob connectivity and type + if tree: verify_tree(entry, its recorded bases) + mark tree as expanded + +The important ordering within `verify_tree` is that entries from +the new tree are collected before the base trees are scanned, but +are processed only afterwards. Trust learned from any base can +therefore eliminate work before recursive verification begins. + +Same-path parent subtrees are passed down as comparison bases +during recursive descent. If no comparison base is available, +the new subtree is verified from scratch. + +Worked example +~~~~~~~~~~~~~~ + +Consider a commit that changes one file under `lib/` and moves an +unchanged subtree from `src/` to `dev/`: + + Parent tree New tree + +-- src/ (aaa) +-- dev/ (aaa) + +-- lib/ (bbb) +-- lib/ (ccc) + +-- foo.c (ddd) +-- foo.c (ddd) + +-- bar.c (eee) +-- bar.c (fff) + +Scanning the parent makes `aaa` trusted even though it moved from +`src/` to `dev/`, so that subtree is skipped. The changed `ccc` +subtree is compared against its same-path parent `bbb`; scanning +`bbb` makes `ddd` and `eee` trusted, leaving only the new `fff` +blob to be checked. + +This illustrates two properties: + +* Trust is OID-based rather than path-based. An unchanged subtree + is recognized after a move. + +* Same-path parent subtrees provide recursive comparison bases. + These bases improve pruning efficiency but are not required for + correctness; a new subtree can always be verified from scratch. + +Multiple parents +~~~~~~~~~~~~~~~~ + +For a merge commit, root trees from all parents are comparison +bases. When several parents contain a same-path subtree, each +matching subtree is collected as a recursive comparison base. + +Entries published from any trusted parent become globally trusted, +so a matching tree or blob entry present in any parent can be +skipped while verifying the merge tree. + +Missing comparison bases +~~~~~~~~~~~~~~~~~~~~~~~~ + +A promised base tree may not be locally available for comparison. +In that case the verifier skips that base and verifies the new +subtree without it. The missing comparison can reduce pruning but +does not affect correctness. diff --git a/Makefile b/Makefile index d4b775953d..aa5b4e2b84 100644 --- a/Makefile +++ b/Makefile @@ -1357,6 +1357,7 @@ LIB_OBJS += trailer.o LIB_OBJS += transport-helper.o LIB_OBJS += transport.o LIB_OBJS += tree-diff.o +LIB_OBJS += tree-verify.o LIB_OBJS += tree-walk.o LIB_OBJS += tree.o LIB_OBJS += unpack-trees.o diff --git a/builtin/rev-list.c b/builtin/rev-list.c index 6b596231ab..beaec67d16 100644 --- a/builtin/rev-list.c +++ b/builtin/rev-list.c @@ -28,6 +28,7 @@ #include "commit-reach.h" #include "quote.h" #include "strbuf.h" +#include "tree-verify.h" struct rev_list_info { struct rev_info *revs; @@ -706,6 +707,7 @@ int cmd_rev_list(int argc, int bisect_find_all = 0; int use_bitmap_index = 0; int filter_provided_objects = 0; + int verify_trees_incremental = 0; const char *show_progress = NULL; int ret = 0; @@ -748,6 +750,9 @@ int cmd_rev_list(int argc, if (!strcmp(arg, "--exclude-promisor-objects")) { repo->fetch_if_missing = 0; revs.exclude_promisor_objects = 1; + } else if (!strcmp(arg, "--verify-trees-incremental")) { + verify_trees_incremental = 1; + repo->fetch_if_missing = 0; } else if (skip_prefix(arg, "--missing=", &arg)) { parse_missing_action_value(repo, arg); } else if (!strcmp(arg, "-z")) { @@ -822,6 +827,8 @@ int cmd_rev_list(int argc, if (!strcmp(arg, "--exclude-promisor-objects")) continue; /* already handled above */ + if (!strcmp(arg, "--verify-trees-incremental")) + continue; /* already handled above */ if (skip_prefix(arg, "--missing=", &arg)) continue; /* already handled above */ @@ -935,6 +942,18 @@ int cmd_rev_list(int argc, prepare_maximal_independent(&revs); + if (verify_trees_incremental) { + struct commit *commit; + struct commit_list *new_commits = NULL; + + while ((commit = get_revision(&revs)) != NULL) + commit_list_insert(commit, &new_commits); + + verify_commits_incremental(repo, &new_commits, + revs.exclude_promisor_objects); + commit_list_free(new_commits); + } + if (revs.tree_objects) mark_edges_uninteresting(&revs, show_edge, 0); diff --git a/connected.c b/connected.c index 929b9bd28d..e3dcd8e2b0 100644 --- a/connected.c +++ b/connected.c @@ -1,6 +1,7 @@ #define USE_THE_REPOSITORY_VARIABLE #include "git-compat-util.h" +#include "config.h" #include "gettext.h" #include "hex.h" #include "odb.h" @@ -67,6 +68,26 @@ static int check_connected_promisor(oid_iterate_fn fn, return 1; } +static int incremental_check_applicable(struct check_connected_options *opt) +{ + const char *algorithm = NULL; + + if (repo_config_get_string_tmp(the_repository, + "transfer.connectivitycheck", + &algorithm)) + return 0; + if (!strcasecmp(algorithm, "full")) + return 0; + if (strcasecmp(algorithm, "incremental")) + die(_("unknown transfer.connectivityCheck algorithm '%s'"), + algorithm); + + if (opt->is_deepening_fetch) + return 0; + + return 1; +} + /* * If we feed all the commits we want to verify to this command * @@ -133,6 +154,9 @@ int check_connected(oid_iterate_fn fn, void *cb_data, if (opt->progress) strvec_pushf(&rev_list.args, "--progress=%s", _("Checking connectivity")); + if (incremental_check_applicable(opt)) + strvec_push(&rev_list.args, + "--verify-trees-incremental"); rev_list.git_cmd = 1; if (opt->env) diff --git a/meson.build b/meson.build index 0a95d90d21..d94dedc26c 100644 --- a/meson.build +++ b/meson.build @@ -562,6 +562,7 @@ libgit_sources = [ 'transport-helper.c', 'transport.c', 'tree-diff.c', + 'tree-verify.c', 'tree-walk.c', 'tree.c', 'unpack-trees.c', diff --git a/t/meson.build b/t/meson.build index 7f53cca7d1..19a8246c44 100644 --- a/t/meson.build +++ b/t/meson.build @@ -652,6 +652,7 @@ integration_tests = [ 't5409-colorize-remote-messages.sh', 't5410-receive-pack.sh', 't5411-proc-receive-hook.sh', + 't5412-connectivity-check.sh', 't5500-fetch-pack.sh', 't5501-fetch-push-alternates.sh', 't5502-quickfetch.sh', diff --git a/t/perf/generate-repo-p5412-connectivity-check.perl b/t/perf/generate-repo-p5412-connectivity-check.perl new file mode 100644 index 0000000000..9546996280 --- /dev/null +++ b/t/perf/generate-repo-p5412-connectivity-check.perl @@ -0,0 +1,44 @@ +#!/usr/bin/perl +# +# Generate a fast-import stream for p5412 connectivity check benchmarks. +# +# Usage: generate-repo-p5412-connectivity-check.perl +# [] [] +# +# Creates one initial commit with dirs*files_per_dir files, then +# additional commits each modifying +# files in directories chosen round-robin from 1... + +use strict; +use warnings; + +my ($nd, $nf, $nc, $hot, $fpc) = @ARGV; +$hot = $nd if !$hot || $hot > $nd; +$fpc = 1 if !$fpc; + +sub data { + printf "data %d\n%s\n", length($_[0]), $_[0]; +} + +# Initial tree: one commit with nd*nf files. +printf "commit refs/heads/main\n"; +printf "committer perf now\n"; +data("initial"); +for my $d (1..$nd) { + for my $f (1..$nf) { + printf "M 100644 inline d-%04d/f-%03d\n", $d, $f; + data(sprintf "%03d%03d", $d, $f); + } +} + +# Subsequent commits (auto-chained by fast-import). +for my $i (1..$nc) { + printf "commit refs/heads/main\n"; + printf "committer perf now\n"; + data(sprintf "change-%03d", $i); + for my $j (0..$fpc-1) { + my $d = (($i + $j) % $hot) + 1; + printf "M 100644 inline d-%04d/f-001\n", $d; + data(sprintf "c%d-%d", $i, $j); + } +} diff --git a/t/perf/p5412-connectivity-check.sh b/t/perf/p5412-connectivity-check.sh new file mode 100755 index 0000000000..827643a847 --- /dev/null +++ b/t/perf/p5412-connectivity-check.sh @@ -0,0 +1,92 @@ +#!/bin/sh + +test_description='performance of connectivity check modes + +Compare the default and incremental rev-list connectivity modes +directly, avoiding pack transfer noise. + +Each repository has a flat tree of many directories with 100 files +in each. Three axes are scaled independently: tree size, commit +count, and files changed per commit.' + +. ./perf-lib.sh + +test_perf_fresh_repo + +generate="$TEST_DIRECTORY/perf/generate-repo-p5412-connectivity-check.perl" + +# $1=dirs $2=files_per_dir $3=commits $4=hot_dirs (optional, default=all) +# $5=files_per_commit (optional, default=1) +test_perf_conn () { + local nd="$1" nf="$2" nc="$3" hot="${4:-$1}" fpc="${5:-1}" + local total=$(($nd * $nf)) + local name="repo-${nd}d-${nf}f-${nc}c-${hot}h-${fpc}fpc" + local label="${total} files, ${nc} commits" + if test "$hot" -lt "$nd" + then + label="$label (${hot} hot dirs)" + fi + if test "$fpc" -gt 1 + then + label="$label (${fpc} files/commit)" + fi + + test_expect_success "setup $label" ' + if test -d '"$name"' + then + true + else + git init '"$name"' && + "$PERL_PATH" '"$generate"' '"$nd"' '"$nf"' '"$nc"' '"$hot"' '"$fpc"' | + git -C '"$name"' fast-import --date-format=now --quiet && + ( + cd '"$name"' && + git rev-parse main~'"$nc"' >../'"${name}"'_old && + git rev-parse main >../'"${name}"'_new && + git update-ref refs/heads/main \ + $(cat ../'"${name}"'_old) && + git repack -ad && + git config gc.auto 0 + ) + fi + ' + + test_perf "$label (full)" ' + cat '"${name}"'_new | + git -C '"$name"' rev-list \ + --objects --stdin --not --all --quiet \ + --exclude-promisor-objects + ' + + test_perf "$label (incremental)" ' + cat '"${name}"'_new | + git -C '"$name"' rev-list --verify-trees-incremental \ + --objects --stdin --not --all --quiet \ + --exclude-promisor-objects + ' +} + +# Scaling tree size (10 commits, 10 files/commit). +test_perf_conn 50 100 10 50 10 +test_perf_conn 500 100 10 500 10 +test_perf_conn 2000 100 10 2000 10 +test_perf_conn 8000 100 10 8000 10 + +# Scaling commit count (200K files, 10 files/commit). +test_perf_conn 2000 100 1 2000 10 +test_perf_conn 2000 100 10 2000 10 +test_perf_conn 2000 100 100 2000 10 +test_perf_conn 2000 100 500 2000 10 +test_perf_conn 2000 100 3000 2000 10 +test_perf_conn 2000 100 5000 2000 10 +test_perf_conn 2000 100 10000 2000 10 + +# Scaling files per commit (200K files, 10 commits). +test_perf_conn 2000 100 10 2000 1 +test_perf_conn 2000 100 10 2000 10 +test_perf_conn 2000 100 10 2000 100 +test_perf_conn 2000 100 10 2000 500 +test_perf_conn 2000 100 10 2000 1000 +test_perf_conn 2000 100 10 2000 2000 + +test_done diff --git a/t/t5412-connectivity-check.sh b/t/t5412-connectivity-check.sh new file mode 100755 index 0000000000..1c84cfe452 --- /dev/null +++ b/t/t5412-connectivity-check.sh @@ -0,0 +1,680 @@ +#!/bin/sh + +test_description='connectivity check (transfer.connectivityCheck)' +GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main +export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME + +. ./test-lib.sh + +test_oid_cache <<-\EOF +missing sha1:0000000000000000000000000000000000000001 +missing sha256:0000000000000000000000000000000000000000000000000000000000000001 +EOF + +set_connectivity_check () { + git -C "$1" config transfer.connectivityCheck "$2" +} + +# Run a connectivity check via rev-list directly. Uses $mode +# (set by the enclosing for-loop) to choose full or incremental. +check_connected () { + flags= && + if test "$mode" = incremental + then + flags=--verify-trees-incremental + fi && + printf '%s\n' "$@" | + git rev-list $flags \ + --objects --stdin --not --all --quiet \ + --exclude-promisor-objects +} + +# Run git with a temporary index, leaving the real index untouched. +tmpgit () { + GIT_INDEX_FILE=.git/tmp-idx git "$@" +} + +# Create a commit with one file changed, without modifying HEAD, +# index, or worktree. Prints the new commit OID on stdout. +# Usage: commit_with_change +commit_with_change () { + new_blob=$(echo "$3" | git hash-object -w --stdin) && + tmpgit read-tree "$1" && + tmpgit update-index --replace \ + --cacheinfo "100644,$new_blob,$2" && + new_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + git commit-tree "$new_tree" -p "$1" -m "modify $2" +} + +# Check OIDs and optionally verify trace2 counts. +# Usage: check_connected_trace ... +# An empty string for or skips that assertion. +check_connected_trace () { + trace_file=$1 trees=$2 blobs=$3 && + shift 3 && + test_env GIT_TRACE2_EVENT="$(pwd)/$trace_file" \ + check_connected "$@" && + if test "$mode" != incremental + then + return + fi && + if test -n "$trees" + then + test_trace2_data_singular connectivity trees_loaded "$trees" \ + <"$trace_file" + fi && + if test -n "$blobs" + then + test_trace2_data_singular connectivity blobs_checked "$blobs" \ + <"$trace_file" + fi +} + +# Shared setup: a repo with several root-level files and nested dirs. +# The unchanged/ subtree (10 dirs x 10 files = 100 blobs, 11 trees) +# acts as a canary: any test asserting small tree/blob counts would +# fail dramatically if incremental accidentally walked into it. + +test_expect_success 'setup main repo' ' + git init main-repo && + ( + cd main-repo && + for i in $(test_seq 1 5) + do + echo "file $i" >"file-$i.txt" || return 1 + done && + git add file-*.txt && + git commit -m "initial" && + + mkdir -p a/b/c && + echo deep >a/b/c/deep.txt && + echo other >a/other.txt && + git add a/b/c/deep.txt a/other.txt && + git commit -m "add nested dirs" && + + for i in $(test_seq 1 10) + do + d="unchanged/dir-$i" && + mkdir -p "$d" && + for j in $(test_seq 1 10) + do + echo "$i $j" >"$d/file-$j.txt" || return 1 + done + done && + git add unchanged/ && + git commit -m "add unchanged canary subtree" + ) +' + +test_expect_success 'setup replacement object repo' ' + git init replace-test && + ( + cd replace-test && + + test_commit --no-tag original file.txt && + original=$(git rev-parse HEAD) && + orig_blob=$(git rev-parse HEAD:file.txt) && + + # Orphan replacement commit with a different tree + replacement_tree=$(echo replaced | git hash-object -w --stdin | + xargs -I{} git mktree <<-EOF + 100644 blob {} file.txt + EOF + ) && + replacement=$(git commit-tree -m "replacement" \ + "$replacement_tree") && + + git replace "$original" "$replacement" && + + # Remove the original blob so only the replacement + # tree is complete. + rm .git/objects/$(test_oid_to_path "$orig_blob") && + + # Drop branch and HEAD so --not --all does not + # exclude the original commit. + git update-ref -d refs/heads/main && + git update-ref -d HEAD && + + echo "$original" >.git/test-oid + ) +' + +missing_oid=$(test_oid missing) +original_oid=$(cat replace-test/.git/test-oid) + +for mode in full incremental +do + +# Corruption detection: craft broken object graphs and verify detection. +# All tests use main-repo without modifying its refs or worktree. + +test_expect_success "$mode: rejects commit with missing blob" ' + ( + cd main-repo && + bad_tree=$(printf "100644 blob ${missing_oid}\tfile.txt\n" | + git mktree --missing) && + bad_commit=$(git commit-tree "$bad_tree" -p HEAD -m "bad") && + test_expect_code 128 check_connected "$bad_commit" 2>err && + test_grep "missing blob object" err + ) +' + +test_expect_success "$mode: rejects commit with missing subtree" ' + ( + cd main-repo && + bad_tree=$(printf "40000 tree ${missing_oid}\tdir\n" | + git mktree --missing) && + bad_commit=$(git commit-tree "$bad_tree" -p HEAD -m "bad") && + test_expect_code 128 check_connected "$bad_commit" 2>err && + test_grep "bad tree object" err + ) +' + +test_expect_success "$mode: verifies direct tree tip" ' + ( + cd main-repo && + bad_tree=$(printf "100644 blob ${missing_oid}\tfile.txt\n" | + git mktree --missing) && + test_expect_code 128 check_connected "$bad_tree" 2>err && + test_grep "missing blob object" err + ) +' + +test_expect_success "$mode: verifies direct blob tip" ' + ( + cd main-repo && + blob_oid=$(echo "hello" | git hash-object -w --stdin) && + check_connected "$blob_oid" + ) +' + +test_expect_success "$mode: rejects missing direct blob tip" ' + ( + cd main-repo && + test_expect_code 128 check_connected \ + "$missing_oid" 2>err + ) +' + +test_expect_success PERL_TEST_HELPERS \ + "$mode: rejects blob OID reused as tree entry" ' + ( + cd main-repo && + + blob_oid=$(git rev-parse HEAD:file-1.txt) && + bin_oid=$(echo "$blob_oid" | hex2oct) && + + bad_tree=$(printf "40000 subdir\0$bin_oid" | + git hash-object -t tree -w --stdin) && + bad_commit=$(git commit-tree -p HEAD -m "child" "$bad_tree") && + + test_expect_code 128 check_connected "$bad_commit" 2>err && + test_grep "not a tree" err + ) +' + +test_expect_success PERL_TEST_HELPERS \ + "$mode: rejects tree OID reused as blob entry" ' + ( + cd main-repo && + + tree_oid=$(git rev-parse HEAD:a) && + bin_oid=$(echo "$tree_oid" | hex2oct) && + + bad_tree=$(printf "100644 fakefile\0$bin_oid" | + git hash-object -t tree -w --stdin) && + bad_commit=$(git commit-tree -p HEAD -m "child" "$bad_tree") && + + test_expect_code 128 check_connected "$bad_commit" 2>err && + test_grep "not a blob" err + ) +' + +test_expect_success "$mode: checks multiple tips" ' + ( + cd main-repo && + c1=$(commit_with_change HEAD file-1.txt "tip-a") && + c2=$(commit_with_change HEAD file-2.txt "tip-b") && + git tag -a -m "tagged" multi-tag "$c1" && + tag_oid=$(git rev-parse multi-tag) && + git tag -d multi-tag && + check_connected "$c2" "$tag_oid" + ) +' + +# Tree-diff optimization: verify trace2 counts. + +test_expect_success "$mode: handles root commit (no parents)" ' + ( + cd main-repo && + blob_oid=$(echo "root-content" | git hash-object -w --stdin) && + tree_oid=$(printf "100644 blob %s\tfile.txt\n" \ + "$blob_oid" | git mktree) && + root_oid=$(git commit-tree "$tree_oid" -m "root") && + + # No parent trees, so the full tree is verified. + # 1 tree loaded (root), 1 blob checked. + check_connected_trace trace-root.txt 1 1 "$root_oid" + ) +' + +test_expect_success "$mode: handles single file change" ' + ( + cd main-repo && + oid=$(commit_with_change HEAD file-1.txt "changed") && + + # 2 trees loaded (new root + parent root), 1 blob checked. + check_connected_trace trace-flat.txt 2 1 "$oid" + ) +' + +test_expect_success "$mode: handles nested change" ' + ( + cd main-repo && + oid=$(commit_with_change HEAD a/b/c/deep.txt "deep-changed") && + # 4 new trees + 4 parent trees = 8 loaded, 1 blob checked. + check_connected_trace trace-nested.txt 8 1 "$oid" + ) +' + +test_expect_success "$mode: handles change-then-revert" ' + ( + cd main-repo && + c1=$(commit_with_change HEAD file-1.txt "revert-tmp") && + c2=$(commit_with_change "$c1" file-1.txt "file 1") && + c3=$(commit_with_change "$c2" file-1.txt "revert-final") && + + # c1: new root + parent root = 2 loads. c2: root matches + # HEAD (already trusted), skipped. c3: new root + parent + # already expanded = 1 load. Total: 3 trees, 2 blobs. + check_connected_trace trace-revert.txt 3 2 "$c3" + ) +' + +test_expect_success "$mode: handles subtree moved to another path" ' + ( + cd main-repo && + moved_tree=$(git ls-tree HEAD | + sed "s/ a$/ moved/" | + git mktree) && + moved=$(git commit-tree "$moved_tree" -p HEAD -m move) && + # New root + parent root scanned, but the moved subtree + # (same OID) is trusted and not descended into. + check_connected_trace trace-move.txt 2 0 "$moved" + ) +' + +test_expect_success "$mode: handles multi-parent merge" ' + ( + cd main-repo && + left=$(commit_with_change HEAD file-1.txt left) && + right=$(commit_with_change HEAD file-2.txt right) && + git update-ref refs/heads/left "$left" && + git update-ref refs/heads/right "$right" && + left_blob=$(git rev-parse "$left:file-1.txt") && + right_blob=$(git rev-parse "$right:file-2.txt") && + tmpgit read-tree HEAD && + tmpgit update-index --replace \ + --cacheinfo "100644,$left_blob,file-1.txt" && + tmpgit update-index --replace \ + --cacheinfo "100644,$right_blob,file-2.txt" && + merge_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + merge=$(git commit-tree "$merge_tree" \ + -p "$left" -p "$right" -m merge) && + # Both parent root trees are scanned as bases, so + # blobs from each parent are trusted without ODB checks. + check_connected_trace trace-merge.txt 3 0 "$merge" && + git update-ref -d refs/heads/left && + git update-ref -d refs/heads/right + ) +' + +test_expect_success "$mode: handles merge with incoming and boundary parents" ' + ( + cd main-repo && + # parent1 is incoming (not a ref), HEAD is boundary. + parent1=$(commit_with_change HEAD file-1.txt merge-inc) && + merge=$(git commit-tree \ + "$(git rev-parse "$parent1^{tree}")" \ + -p "$parent1" -p HEAD -m merge-mixed) && + # parent1 verified first (topo order): 2 trees, 1 blob. + # merge tree = parent1 tree (already trusted): 0 extra. + check_connected_trace trace-merge-inc.txt 2 1 "$merge" + ) +' + +test_expect_success "$mode: handles gitlink entries (submodules)" ' + ( + cd main-repo && + tmpgit read-tree HEAD && + tmpgit update-index --add \ + --cacheinfo "160000,$missing_oid,my-submodule" && + gitlink_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + gitlink_commit=$(git commit-tree "$gitlink_tree" -p HEAD \ + -m "add gitlink") && + + # Gitlink entries are skipped -- the missing submodule + # commit OID does not cause a failure. + check_connected_trace trace-gitlink.txt 2 0 "$gitlink_commit" + ) +' + +test_expect_success "$mode: handles file-to-directory transition" ' + ( + cd main-repo && + + # Parent: "foo" is a blob at root. + blob_a=$(echo "file-content" | git hash-object -w --stdin) && + tmpgit read-tree HEAD && + tmpgit update-index --add \ + --cacheinfo "100644,$blob_a,foo" && + parent_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + parent=$(git commit-tree "$parent_tree" -p HEAD \ + -m "add foo as file") && + + # Child: "foo" becomes a directory (foo/bar.txt). + blob_b=$(echo "dir-content" | git hash-object -w --stdin) && + tmpgit read-tree "$parent" && + tmpgit update-index --remove foo && + tmpgit update-index --add \ + --cacheinfo "100644,$blob_b,foo/bar.txt" && + child_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + child=$(git commit-tree "$child_tree" -p "$parent" \ + -m "foo: file to directory") && + check_connected_trace trace-f2d.txt "" "" "$child" + ) +' + +test_expect_success "$mode: handles directory-to-file transition" ' + ( + cd main-repo && + + # Parent: "bar/baz.txt" exists (bar is a directory). + blob_a=$(echo "nested" | git hash-object -w --stdin) && + tmpgit read-tree HEAD && + tmpgit update-index --add \ + --cacheinfo "100644,$blob_a,bar/baz.txt" && + parent_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + parent=$(git commit-tree "$parent_tree" -p HEAD \ + -m "add bar as directory") && + + # Child: "bar" becomes a plain file. + blob_b=$(echo "flat" | git hash-object -w --stdin) && + tmpgit read-tree "$parent" && + tmpgit update-index --remove bar/baz.txt && + tmpgit update-index --add \ + --cacheinfo "100644,$blob_b,bar" && + child_tree=$(tmpgit write-tree) && + rm -f .git/tmp-idx && + child=$(git commit-tree "$child_tree" -p "$parent" \ + -m "bar: directory to file") && + check_connected_trace trace-d2f.txt "" "" "$child" + ) +' + +# Replacement objects. + +test_expect_success "$mode: accepts with replacement objects" ' + ( + cd replace-test && + check_connected "$original_oid" + ) +' + +test_expect_success "$mode: rejects without replacement objects" ' + ( + cd replace-test && + GIT_NO_REPLACE_OBJECTS=1 && + export GIT_NO_REPLACE_OBJECTS && + test_expect_code 128 check_connected \ + "$original_oid" 2>err && + test_grep "missing blob object" err + ) +' + +test_expect_success "$mode: accepts missing promised blob" ' + test_when_finished "rm -rf prom-src prom-server.git prom-client" && + git init prom-src && + test_commit -C prom-src --no-tag base file.txt original && + test_commit -C prom-src --no-tag "add file2" file2.txt extra && + git clone --bare prom-src prom-server.git && + git -C prom-server.git config uploadpack.allowfilter true && + git -C prom-server.git config uploadpack.allowanysha1inwant true && + git clone --no-checkout --filter=blob:none \ + "file://$(pwd)/prom-server.git" prom-client && + ( + cd prom-client && + promised_blob=$(git rev-parse HEAD:file2.txt) && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_blob" && + new_tree=$(printf "100644 blob %s\tnewname.txt\n" \ + "$promised_blob" | + git mktree --missing) && + new_commit=$(git commit-tree "$new_tree" \ + -p HEAD -m "reuse promised blob") && + check_connected "$new_commit" && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_blob" + ) +' + +test_expect_success "$mode: does not lazy-fetch promised blob" ' + test_when_finished "rm -rf nofetch-src nofetch-server.git nofetch-client" && + git init nofetch-src && + test_commit -C nofetch-src --no-tag base file.txt content && + git clone --bare nofetch-src nofetch-server.git && + git -C nofetch-server.git config uploadpack.allowfilter true && + git -C nofetch-server.git config uploadpack.allowanysha1inwant true && + git clone --no-checkout --filter=blob:none \ + "file://$(pwd)/nofetch-server.git" nofetch-client && + ( + cd nofetch-client && + promised_blob=$(git rev-parse HEAD:file.txt) && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_blob" && + new_tree=$(printf "100644 blob %s\tfile.txt\n" \ + "$promised_blob" | + git mktree --missing) && + new_commit=$(git commit-tree "$new_tree" \ + -m "root commit with promised blob") && + check_connected "$new_commit" && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_blob" + ) +' + +test_expect_success "$mode: accepts missing promised tree" ' + test_when_finished "rm -rf prom-tree-src prom-tree-server.git prom-tree-client" && + git init prom-tree-src && + mkdir -p prom-tree-src/a/b && + test_commit -C prom-tree-src --no-tag "nested dirs" a/b/file.txt deep && + git clone --bare prom-tree-src prom-tree-server.git && + git -C prom-tree-server.git config uploadpack.allowfilter true && + git -C prom-tree-server.git config uploadpack.allowanysha1inwant true && + git clone --no-checkout --filter=tree:1 \ + "file://$(pwd)/prom-tree-server.git" prom-tree-client && + ( + cd prom-tree-client && + promised_tree=$(git ls-tree HEAD -- a | + awk "{print \$3}") && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_tree" && + new_tree=$(printf "40000 tree %s\trenamed\n" \ + "$promised_tree" | + git mktree --missing) && + new_commit=$(git commit-tree "$new_tree" \ + -p HEAD -m "reuse promised tree") && + check_connected "$new_commit" && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$promised_tree" + ) +' + +test_expect_success "$mode: verifies new subtree when parent subtree is promised" ' + test_when_finished "rm -rf prom-base-src prom-base-server.git prom-base-client" && + git init prom-base-src && + mkdir -p prom-base-src/a && + test_commit -C prom-base-src --no-tag "base" a/file.txt deep && + git clone --bare prom-base-src prom-base-server.git && + git -C prom-base-server.git config uploadpack.allowfilter true && + git -C prom-base-server.git config uploadpack.allowanysha1inwant true && + git clone --no-checkout --filter=tree:1 \ + "file://$(pwd)/prom-base-server.git" prom-base-client && + ( + cd prom-base-client && + parent_subtree=$(git ls-tree HEAD -- a | + awk "{print \$3}") && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$parent_subtree" && + new_blob=$(echo "local-content" | git hash-object -w --stdin) && + new_subtree=$(printf "100644 blob %s\tfile.txt\n" \ + "$new_blob" | git mktree) && + new_root=$(printf "40000 tree %s\ta\n" \ + "$new_subtree" | git mktree) && + new_commit=$(git commit-tree "$new_root" \ + -p HEAD -m "replace promised subtree") && + check_connected "$new_commit" && + test_must_fail env GIT_NO_LAZY_FETCH=1 \ + git cat-file -e "$parent_subtree" + ) +' + +test_expect_success "$mode: verifies local commit in partial clone" ' + test_when_finished "rm -rf pc-src pc-server.git pc-client" && + git init pc-src && + test_commit -C pc-src --no-tag base file.txt && + git clone --bare pc-src pc-server.git && + git -C pc-server.git config uploadpack.allowfilter true && + git -C pc-server.git config uploadpack.allowanysha1inwant true && + git clone --filter=blob:none \ + "file://$(pwd)/pc-server.git" pc-client && + ( + cd pc-client && + local_commit=$(commit_with_change HEAD file.txt local-content) && + check_connected "$local_commit" + ) +' + +test_expect_success "$mode: respects shallow boundary" ' + test_when_finished "rm -rf shallow-src shallow" && + git init shallow-src && + test_commit -C shallow-src --no-tag base file content-1 && + mkdir shallow-src/sub && + test_commit -C shallow-src --no-tag change sub/other content-2 && + git clone --depth=1 "file://$(pwd)/shallow-src" shallow && + ( + cd shallow && + tip=$(git rev-parse HEAD) && + git for-each-ref --format="delete %(refname)" | + git update-ref --no-deref --stdin && + check_connected "$tip" + ) +' + +test_expect_success "$mode: deepening fetch succeeds" ' + test_when_finished "rm -rf deepen-src deepen-server.git deepen-client" && + git init deepen-src && + test_commit -C deepen-src --no-tag c1 file.txt && + test_commit -C deepen-src --no-tag c2 file.txt && + test_commit -C deepen-src --no-tag c3 file.txt && + git clone --bare deepen-src deepen-server.git && + git clone --depth=1 "file://$(pwd)/deepen-server.git" deepen-client && + set_connectivity_check deepen-client $mode && + test -f deepen-client/.git/shallow && + GIT_TRACE2_EVENT="$(pwd)/deepen-trace.txt" \ + git -C deepen-client fetch --deepen=2 origin main && + # Incremental falls back to full for deepening fetches, + # so the trees_loaded event should not appear. + test_grep ! trees_loaded deepen-trace.txt +' + +test_expect_success "$mode: malformed tree detected" ' + ( + cd main-repo && + echo abc >malformed-tree && + malformed_tree=$(git hash-object --literally -t tree -w \ + malformed-tree) && + malformed_commit=$(git commit-tree "$malformed_tree" \ + -p HEAD -m malformed) && + test_expect_code 128 check_connected \ + "$malformed_commit" 2>err + ) +' + +test_expect_success PERL_TEST_HELPERS \ + "$mode: mid-tree corruption detected" ' + ( + cd main-repo && + # Build a tree with one valid entry followed by garbage. + blob_oid=$(echo "valid" | git hash-object -w --stdin) && + bin_oid=$(echo "$blob_oid" | hex2oct) && + printf "100644 good\0${bin_oid}GARBAGE" >corrupt-mid-tree && + corrupt_tree=$(git hash-object --literally -t tree -w \ + corrupt-mid-tree) && + corrupt_commit=$(git commit-tree "$corrupt_tree" \ + -p HEAD -m "mid-tree corruption") && + test_expect_code 128 check_connected \ + "$corrupt_commit" 2>err && + test_grep "too-short tree object" err + ) +' + +done + +# Algorithm selection. + +test_expect_success 'invalid transfer.connectivityCheck is rejected' ' + test_when_finished "rm -rf invalid-cfg-src invalid-cfg-dst" && + git init invalid-cfg-src && + test_commit -C invalid-cfg-src --no-tag base file.txt && + git clone invalid-cfg-src invalid-cfg-dst && + test_commit -C invalid-cfg-src --no-tag update file.txt updated && + git -C invalid-cfg-dst config transfer.connectivityCheck bogus && + test_must_fail git -C invalid-cfg-dst fetch origin main 2>err && + test_grep "unknown transfer.connectivityCheck" err +' + +test_expect_success 'push uses incremental when configured' ' + test_when_finished "rm -rf int-src int-dst.git" && + git init int-src && + test_commit -C int-src --no-tag base file.txt && + git clone --bare int-src int-dst.git && + test_commit -C int-src --no-tag update file.txt updated && + set_connectivity_check int-dst.git incremental && + GIT_TRACE2_EVENT="$(pwd)/push-trace.txt" \ + git -C int-src push ../int-dst.git main && + test_trace2_data_singular connectivity trees_loaded 2 \ + kh_val(m, pos)) + kh_val(m, pos) = state; +} + +struct work_item { + struct name_entry entry; + struct oid_array parent_trees; +}; + +struct verify_state { + kh_oid_tree_t *trees; + struct oidset trusted_blobs; + int trees_loaded; + int blobs_checked; + int exclude_promisor_objects; +}; + +/* + * Merge-walk the work list against one base tree entry, recording + * same-path parent subtrees as recursive comparison bases. + * Returns the updated work-list cursor. + */ +static size_t collect_subtree_bases(struct work_item *work, size_t nr_work, + size_t wi, const struct name_entry *entry) +{ + while (wi < nr_work) { + int cmp = base_name_compare( + work[wi].entry.path, work[wi].entry.pathlen, + work[wi].entry.mode, + entry->path, entry->pathlen, + entry->mode); + if (cmp > 0) + break; + if (cmp < 0) { + wi++; + continue; + } + if (S_ISDIR(work[wi].entry.mode) && + S_ISDIR(entry->mode)) + oid_array_append(&work[wi].parent_trees, + &entry->oid); + return wi + 1; + } + return wi; +} + +static void verify_blob(struct repository *repo, + const struct object_id *oid, + struct verify_state *vs) +{ + int type; + + if (oidset_contains(&vs->trusted_blobs, oid)) + return; + + vs->blobs_checked++; + type = odb_read_object_info(repo->objects, oid, NULL); + if (type == OBJ_BLOB) { + oidset_insert(&vs->trusted_blobs, oid); + return; + } + if (type >= 0) + die(_("object %s is a %s, not a %s"), + oid_to_hex(oid), type_name(type), "blob"); + if (vs->exclude_promisor_objects && + is_promisor_object(repo, oid)) + return; + die(_("missing blob object '%s'"), oid_to_hex(oid)); +} + +static void *read_tree_object(struct object_database *odb, + const struct object_id *oid, + size_t *sizep) +{ + enum object_type type; + void *buf = odb_read_object(odb, oid, &type, sizep); + + if (buf && type != OBJ_TREE) { + free(buf); + die(_("object %s is a %s, not a %s"), + oid_to_hex(oid), type_name(type), "tree"); + } + return buf; +} + +static void verify_tree(struct repository *repo, + const struct object_id *new_tree_oid, + const struct oid_array *base_trees, + struct verify_state *vs, int depth) +{ + struct tree_desc desc; + struct name_entry entry; + struct work_item *work = NULL; + size_t nr_work = 0, alloc_work = 0; + int need_subtree_bases = 0; + size_t i, tree_size; + void *tree_buf; + + if (depth > repo->settings.max_allowed_tree_depth) + die(_("exceeded maximum allowed tree depth")); + + if (tree_map_get(vs->trees, new_tree_oid) >= TREE_TRUSTED) + return; + + tree_buf = read_tree_object(repo->objects, new_tree_oid, &tree_size); + if (!tree_buf) { + if (vs->exclude_promisor_objects && + is_promisor_object(repo, new_tree_oid)) + return; + die(_("bad tree object %s"), + oid_to_hex(new_tree_oid)); + } + + vs->trees_loaded++; + init_tree_desc(&desc, new_tree_oid, tree_buf, tree_size); + + while (tree_entry(&desc, &entry)) { + if (S_ISGITLINK(entry.mode)) + continue; + if (S_ISDIR(entry.mode)) { + if (tree_map_get(vs->trees, &entry.oid) >= TREE_TRUSTED) + continue; + need_subtree_bases = 1; + } else { + if (oidset_contains(&vs->trusted_blobs, &entry.oid)) + continue; + } + ALLOC_GROW(work, nr_work + 1, alloc_work); + memset(&work[nr_work], 0, sizeof(work[nr_work])); + work[nr_work].entry = entry; + nr_work++; + } + + if (!nr_work) { + free(tree_buf); + goto done; + } + + for (i = 0; base_trees && i < base_trees->nr; i++) { + const struct object_id *base_oid = &base_trees->oid[i]; + int expanded = tree_map_get(vs->trees, base_oid) >= TREE_EXPANDED; + struct tree_desc base_desc; + struct name_entry scan_entry; + size_t wi = 0, base_size; + void *base_buf; + + if (expanded && !need_subtree_bases) + continue; + + base_buf = read_tree_object(repo->objects, base_oid, + &base_size); + if (!base_buf) { + if (vs->exclude_promisor_objects && + is_promisor_object(repo, base_oid)) + continue; + die(_("bad tree object %s"), + oid_to_hex(base_oid)); + } + + vs->trees_loaded++; + init_tree_desc(&base_desc, base_oid, base_buf, base_size); + + while (tree_entry(&base_desc, &scan_entry)) { + if (S_ISGITLINK(scan_entry.mode)) + continue; + + if (need_subtree_bases) + wi = collect_subtree_bases(work, nr_work, + wi, &scan_entry); + + if (!expanded) { + if (S_ISDIR(scan_entry.mode)) + tree_map_add(vs->trees, + &scan_entry.oid, + TREE_TRUSTED); + else + oidset_insert(&vs->trusted_blobs, + &scan_entry.oid); + } + } + + if (!expanded) + tree_map_add(vs->trees, base_oid, TREE_EXPANDED); + + free(base_buf); + } + + for (i = 0; i < nr_work; i++) { + if (S_ISDIR(work[i].entry.mode)) + verify_tree(repo, &work[i].entry.oid, + &work[i].parent_trees, vs, + depth + 1); + else + verify_blob(repo, &work[i].entry.oid, vs); + } + + free(tree_buf); + +done: + tree_map_add(vs->trees, new_tree_oid, TREE_EXPANDED); + for (i = 0; i < nr_work; i++) + oid_array_clear(&work[i].parent_trees); + free(work); +} + +static void verify_commit_tree(struct repository *repo, + struct commit *commit, + struct verify_state *vs) +{ + struct oid_array base_trees = OID_ARRAY_INIT; + struct commit_list *p; + + /* + * Parent trees are trusted: boundary parents are already + * connected, and earlier incoming parents were verified + * first due to the topological processing order. + */ + for (p = commit->parents; p; p = p->next) { + const struct object_id *tree_oid; + parse_commit_or_die(p->item); + tree_oid = get_commit_tree_oid(p->item); + if (!tree_oid) + die(_("unable to load root tree for commit %s"), + oid_to_hex(&p->item->object.oid)); + tree_map_add(vs->trees, tree_oid, TREE_TRUSTED); + oid_array_append(&base_trees, tree_oid); + } + + if (!get_commit_tree_oid(commit)) + die(_("unable to load root tree for commit %s"), + oid_to_hex(&commit->object.oid)); + verify_tree(repo, get_commit_tree_oid(commit), + &base_trees, vs, 0); + oid_array_clear(&base_trees); +} + +void verify_commits_incremental(struct repository *repo, + struct commit_list **commits, + int exclude_promisor_objects) +{ + struct verify_state vs = { 0 }; + struct commit_list *iter; + unsigned nr_before; + + if (repo->fetch_if_missing) + BUG("verify_commits_incremental must not be called " + "with fetch_if_missing set"); + + vs.trees = kh_init_oid_tree(); + vs.exclude_promisor_objects = exclude_promisor_objects; + + /* + * Ancestors must be verified before descendants so that parent + * trees can be trusted without re-verification. Sort explicitly + * rather than relying on the caller's ordering. + * + * sort_in_topological_order() silently drops cycle members, + * so explicitly check if the size has changed. + */ + nr_before = commit_list_count(*commits); + sort_in_topological_order(commits, REV_SORT_IN_GRAPH_ORDER); + if (commit_list_count(*commits) < nr_before) + die(_("cycle detected in incoming commit graph")); + + *commits = commit_list_reverse(*commits); + + for (iter = *commits; iter; iter = iter->next) + verify_commit_tree(repo, iter->item, &vs); + + kh_destroy_oid_tree(vs.trees); + oidset_clear(&vs.trusted_blobs); + trace2_data_intmax("connectivity", repo, + "trees_loaded", vs.trees_loaded); + trace2_data_intmax("connectivity", repo, + "blobs_checked", vs.blobs_checked); +} diff --git a/tree-verify.h b/tree-verify.h new file mode 100644 index 0000000000..6aadadff70 --- /dev/null +++ b/tree-verify.h @@ -0,0 +1,15 @@ +#ifndef TREE_VERIFY_H +#define TREE_VERIFY_H + +struct commit_list; +struct repository; + +/* + * Verify trees of commits incrementally against their parents. + * Dies on verification failure. + */ +void verify_commits_incremental(struct repository *repo, + struct commit_list **commits, + int exclude_promisor_objects); + +#endif /* TREE_VERIFY_H */ -- gitgitgadget ``` ## Patrick Steinhardt, 2026-10-05 07:59 Subject: Re: [PATCH v2 1/2] Documentation: describe connectivity checking Message-ID: In-Reply-To: <97c11449aeae924436ba22a00a2545254e988a58.1790600552.git.gitgitgadget@gmail.com> ``` On Mon, Sep 28, 2026 at 01:02:31PM +0000, Kristofer Karlsson via GitGitGadget wrote: > diff --git a/Documentation/technical/connectivity-check.adoc b/Documentation/technical/connectivity-check.adoc > new file mode 100644 > index 0000000000..d20bff6af6 > --- /dev/null > +++ b/Documentation/technical/connectivity-check.adoc > @@ -0,0 +1,109 @@ > +Connectivity checking > +===================== > + > +After receiving new objects via fetch, push (receive-pack), clone, > +or bundle, Git verifies that the new reference tips do not leave > +the repository in a state where reachable objects are missing. > +This verification is called the connectivity check. > + > +Connectivity invariant > +---------------------- > + > +A repository is connected when every object reachable from its > +references is available locally (with exceptions noted below). Right. I think it would also be important to spell out the reverse of this, which is that nothing can be assumed about objects that aren't reachable by any reference. So even if an object already exists in the object database, it is not safe to assume that it is fully connected unless it is referenced. > +The connectivity check maintains this invariant when references > +are updated. It trusts the existing connected state and verifies Nit: it's basically already implicit, but I'd clarify that "existing connected state" is again just the connected state of objects reachable from reference tips. So maybe "It trusts that all objects reachable from references are already fully connected and verifies..." > +that the new reference tips do not introduce references to > +unavailable objects. Verification is permitted to stop when it > +reaches objects already reachable from trusted existing > +references, since their closure is already connected. These > +trusted references include local references and references from > +alternate object stores. > + > +Without this check, a truncated or corrupted transfer could leave > +a repository in a state where later history walks encounter > +missing objects. > + > +Exceptions > +~~~~~~~~~~ > + > +Gitlink entries (submodule references) are excluded from > +connectivity checking. Their target objects belong to a separate > +repository. > + > +In partial clones, objects promised by a promisor remote are > +accepted as connected without requiring local existence. The > +check excludes promisor objects from traversal so that it does > +not trigger on-demand fetches for them. > + > +Full connectivity check > +----------------------- > + > +`check_connected()` (see `connected.c`) normally performs the I'm always a bit hesitant to directly refer to code in our docs. We should either make this documentation part of "connected.c" directly, or we should not refer to code. Otherwise, chances that this documentation grows stale is very high. > +connectivity check using a `rev-list` subprocess, feeding the > +new reference tips via stdin. A normal invocation is roughly: > + > + git rev-list --objects --stdin --not --all --quiet > + --alternate-refs [--exclude-promisor-objects] > + > +When promisor remotes are configured, `check_connected()` first > +attempts a fast path based on promisor packfiles. If it falls > +back to the `rev-list` check, `--exclude-promisor-objects` is > +added so that the traversal does not trigger on-demand fetches. > + > +Consider the following graph after a fetch, where all reference > +tips point directly to commits. For simplicity, only local > +references appear on the already-connected side; alternate refs > +play the same role. N3 is a merge commit: > + > + /-------------L2 > + / > + C1---B1---C2---B2-----L1 > + \ \ > + N1 N3---T2 > + \ / > + N2-----------T1 > + > + L1, L2: local refs > + T1, T2: incoming tips (new refs) > + N1, N2, N3: incoming commits (N3 is a merge) > + B1, B2: boundary commits (already connected) > + C1, C2: already connected (but not boundary) > + > +The incoming set is the commits reachable from the incoming > +tips but not from the already-connected side. Boundary commits > +are the already-connected commits at the edge of that set. Here > +B1 is an ancestor of B2, which happens when incoming branches > +fork at different depths in the existing history. > + > +The check proceeds in three phases: > + > +1. Walk from the incoming tips (T1, T2) against the trusted > + refs (L1, L2) to find the incoming set ({N1, N2, N3, T1, T2}). > + > +2. Walk the trees of the boundary commits (B1, B2) and mark > + those objects uninteresting. These trees are already trusted > + because their commits are on the already-connected side. > + > +3. Walk the trees of each incoming commit and verify that every > + referenced object is connected, stopping at objects already > + marked uninteresting in phase 2. I feel like these phases here basically just explain how revision walks work without adding any more details that are specifically relevant to the connectivity check. > +Deepening fetches > +~~~~~~~~~~~~~~~~~ > + > +For deepening fetches (where the shallow boundary moves), the > +full check omits `--not --all`. There is no existing-reference > +boundary at which the walk can stop. Instead, traversal follows > +the effective shallow boundary supplied for the deepened > +repository. The new content may be below the old shallow > +boundary even when the tips themselves have not changed. > + > +Non-commit tips > +~~~~~~~~~~~~~~~ > + > +When a new reference points to a non-commit object, such as a > +tag, tree, or blob, that object is not part of the commit walk. > +These non-commit tips are handled by the subsequent object > +traversal. Huh, what subsequent object traversal? This part puzzles me a bit. Patrick ``` ## Patrick Steinhardt, 2026-10-05 08:00 Subject: Re: [PATCH v2 2/2] connected: add incremental connectivity check via rev-list Message-ID: In-Reply-To: <6ad528f4bb42a960910eb4fe917a3766fa55d598.1790600552.git.gitgitgadget@gmail.com> ``` On Mon, Sep 28, 2026 at 01:02:32PM +0000, Kristofer Karlsson via GitGitGadget wrote: > From: Kristofer Karlsson > > The full connectivity check uses rev-list to find commits > reachable from the incoming tips but not from the > already-connected side, then walks their object closure. Commit > traversal stops at the connectivity boundary, but trees and blobs > reachable from that boundary still need to be walked so they can > be marked uninteresting, allocating a struct object for each one. > On repositories where the boundary commits have large trees, the > connectivity check for small incoming changes visits and tracks > more objects than needed. Okay. In the old world we basically mark evertyhing as uninteresting, including trees and blobs, ... > Add an alternative connectivity check that verifies incoming > commits incrementally against their parents. > > The verifier processes incoming commits with ancestors first and > compares each new tree against its trusted parent trees. Entries > already seen on the trusted side are skipped by OID, so unchanged > subtrees need not remain at the same path to be recognized. > Changed subtrees are recursively compared against same-path parent > subtrees, and new subtrees without a comparison base are verified > from scratch. ... whereas in the new world you propose to skip marking trees/blobs as uninteresting. Instead, the idea is to compare the trees/blobs of the old tips directly with the trees/blobs of the new tips and only verify those parts that have changed between the two? This can of course cause us to verify significantly more objects in some scenarios. But it does have the consequence that we scale with the number of changes, not with the number of preexisting objects in the repository. And that's something I'd really appreciate, because marking reachable objects as uninteresting is extremely expensive. One thing I wonder though... does this help with the scenario where we have tons of references or do we still end up passing "--not --all"? I have seen many times that parsing the refs by itself is dominating the time of the connectivity check quite significantly. So ideally, I'd like to have a solution that also catches this case. Your benchmarks do not cover that scenario though. > Incremental uses substantially less memory when it can prune > most of the boundary tree walk. In the long-history case the > two modes visit similar object sets and memory converges. > > The regression cases in the CPU benchmarks are in wall-clock > time rather than memory, primarily from scanning some trees > more than once. > > Signed-off-by: Kristofer Karlsson > --- > Documentation/config/transfer.adoc | 20 + > Documentation/rev-list-options.adoc | 6 + > .../technical/connectivity-check.adoc | 134 ++++ > Makefile | 1 + > builtin/rev-list.c | 19 + > connected.c | 24 + > meson.build | 1 + > t/meson.build | 1 + > ...enerate-repo-p5412-connectivity-check.perl | 44 ++ > t/perf/p5412-connectivity-check.sh | 92 +++ > t/t5412-connectivity-check.sh | 680 ++++++++++++++++++ > tree-verify.c | 316 ++++++++ > tree-verify.h | 15 + > 13 files changed, 1353 insertions(+) > create mode 100644 t/perf/generate-repo-p5412-connectivity-check.perl > create mode 100755 t/perf/p5412-connectivity-check.sh > create mode 100755 t/t5412-connectivity-check.sh > create mode 100644 tree-verify.c > create mode 100644 tree-verify.h May I suggest splitting up this patch in the following way? - One commit that introduces the new option, but for now only accepts "full" as the algorithm. - One commit that introduces the benchmark. - One commit that introduces the new flag for git-rev-list(1). - One commit that then introduces the new strategy. That may make it a bit easier to focus on the actual change. > diff --git a/Documentation/technical/connectivity-check.adoc b/Documentation/technical/connectivity-check.adoc > index d20bff6af6..0a8f370546 100644 > --- a/Documentation/technical/connectivity-check.adoc > +++ b/Documentation/technical/connectivity-check.adoc > @@ -107,3 +107,137 @@ When a new reference points to a non-commit object, such as a > tag, tree, or blob, that object is not part of the commit walk. > These non-commit tips are handled by the subsequent object > traversal. > + > +Incremental connectivity check > +------------------------------ > + > +The incremental mode, selected by > +`transfer.connectivityCheck=incremental`, avoids traversing the > +full tree walk of the boundary commits. Instead, it verifies > +each incoming commit's tree against the already-trusted trees of > +its parents. Can we define "parents" here? Specifically, I wonder how you define "parent" in the case where you perform a force push or when creating a new reference. Is it the parent of the first new commit? Is it the old state of the ref, if it even exists? > +Trust model > +~~~~~~~~~~~ > + > +A tree is trusted when its transitive object closure is known to > +be connected. Trees reachable from commits on the > +already-connected side of the boundary are therefore trusted. Where the "already-connected side of the boundary" is anything reachable via a reference. > +Incoming commits are processed with ancestors before descendants. > +Once an incoming commit's tree has been verified, it is trusted > +and can be used as a comparison base for later descendants. > + > +This gives an inductive correctness argument: every parent of the > +commit currently being verified is either already connected or is > +an earlier incoming commit whose tree has already been verified. Right. The big question to me still is how you identify already-connected trees without having to read all references. > +Worked example Worked? [snip] > diff --git a/tree-verify.c b/tree-verify.c > new file mode 100644 > index 0000000000..5c11c2251a > --- /dev/null > +++ b/tree-verify.c > @@ -0,0 +1,316 @@ [snip] > +static void verify_commit_tree(struct repository *repo, > + struct commit *commit, > + struct verify_state *vs) > +{ > + struct oid_array base_trees = OID_ARRAY_INIT; > + struct commit_list *p; > + > + /* > + * Parent trees are trusted: boundary parents are already > + * connected, and earlier incoming parents were verified > + * first due to the topological processing order. > + */ I feel like I still miss where exactly you establish the trust boundary between preexisting fully-connected commits and new commits. > + for (p = commit->parents; p; p = p->next) { > + const struct object_id *tree_oid; > + parse_commit_or_die(p->item); > + tree_oid = get_commit_tree_oid(p->item); > + if (!tree_oid) > + die(_("unable to load root tree for commit %s"), > + oid_to_hex(&p->item->object.oid)); > + tree_map_add(vs->trees, tree_oid, TREE_TRUSTED); > + oid_array_append(&base_trees, tree_oid); > + } > + > + if (!get_commit_tree_oid(commit)) > + die(_("unable to load root tree for commit %s"), > + oid_to_hex(&commit->object.oid)); > + verify_tree(repo, get_commit_tree_oid(commit), > + &base_trees, vs, 0); > + oid_array_clear(&base_trees); > +} > + > +void verify_commits_incremental(struct repository *repo, > + struct commit_list **commits, > + int exclude_promisor_objects) > +{ > + struct verify_state vs = { 0 }; > + struct commit_list *iter; > + unsigned nr_before; > + > + if (repo->fetch_if_missing) > + BUG("verify_commits_incremental must not be called " > + "with fetch_if_missing set"); > + > + vs.trees = kh_init_oid_tree(); > + vs.exclude_promisor_objects = exclude_promisor_objects; > + > + /* > + * Ancestors must be verified before descendants so that parent > + * trees can be trusted without re-verification. Sort explicitly > + * rather than relying on the caller's ordering. > + * > + * sort_in_topological_order() silently drops cycle members, > + * so explicitly check if the size has changed. > + */ > + nr_before = commit_list_count(*commits); > + sort_in_topological_order(commits, REV_SORT_IN_GRAPH_ORDER); > + if (commit_list_count(*commits) < nr_before) > + die(_("cycle detected in incoming commit graph")); I don't think we should just die, should we? That may not interact well with git-receive-pack(1) and others that expect a broken connectivity check to bubble up errors so that they can properly report those to the client and clean up their local state. > + *commits = commit_list_reverse(*commits); > + > + for (iter = *commits; iter; iter = iter->next) > + verify_commit_tree(repo, iter->item, &vs); > + kh_destroy_oid_tree(vs.trees); > + oidset_clear(&vs.trusted_blobs); > + trace2_data_intmax("connectivity", repo, > + "trees_loaded", vs.trees_loaded); > + trace2_data_intmax("connectivity", repo, > + "blobs_checked", vs.blobs_checked); > +} Patrick ``` ## Junio C Hamano, 2026-10-05 19:17 Subject: Re: [PATCH v2 1/2] Documentation: describe connectivity checking Message-ID: In-Reply-To: ``` Patrick Steinhardt writes: >> +Full connectivity check >> +----------------------- >> + >> +`check_connected()` (see `connected.c`) normally performs the > > I'm always a bit hesitant to directly refer to code in our docs. We > should either make this documentation part of "connected.c" directly, or > we should not refer to code. Otherwise, chances that this documentation > grows stale is very high. This is totally outside the topic of documentation updates, but it makes me wonder if we should pay attention to connectivity roots other than refs (like index entries) that we use when we run fsck. ``` ## Patrick Steinhardt, 2026-10-06 05:59 Subject: Re: [PATCH v2 1/2] Documentation: describe connectivity checking Message-ID: In-Reply-To: ``` On Mon, Oct 05, 2026 at 12:17:27PM -0700, Junio C Hamano wrote: > Patrick Steinhardt writes: > > >> +Full connectivity check > >> +----------------------- > >> + > >> +`check_connected()` (see `connected.c`) normally performs the > > > > I'm always a bit hesitant to directly refer to code in our docs. We > > should either make this documentation part of "connected.c" directly, or > > we should not refer to code. Otherwise, chances that this documentation > > grows stale is very high. > > This is totally outside the topic of documentation updates, but it > makes me wonder if we should pay attention to connectivity roots > other than refs (like index entries) that we use when we run fsck. Hmm, I'm not sure. I guess performance of the connectivity check is typically an issue on the server side only, much less so on the client side. And the server would of course typically not even have an index entry at all. Same for reflogs, at least in many setups. I also wonder whether that'd really speed things up if we add more data sources. At GitLab we typically have the problem that we have too many connectivity roots with refs alone, and that is making the whole check painfully slow in some repositories. So adding more connectivity roots to it would probably be counterproductive. Patrick ```