[PATCH v3 04/11] Prepare `paint_down_to_common()` for handling shallow commits
- From
Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
- Date
- Feb 27, 2024, 13:28 UTC
- Message-ID
- <84e7fbc07e08956e6c493baf499fee455887b16c.1709040499.git.gitgitgadget@gmail.com>
- In-Reply-To
- <pull.1657.v3.git.1709040497.gitgitgadget@gmail.com>
From: Johannes Schindelin <johannes.schindelin@gmx.de>
When `git fetch --update-shallow` needs to test for commit ancestry, it can naturally run into a missing object (e.g. if it is a parent of a shallow commit). To accommodate, the merge base logic will need to be able to handle this situation gracefully.
Currently, that logic pretends that a missing parent commit is equivalent to a missing parent commit, and for the purpose of `--update-shallow` that is exactly what we need it to do.
Therefore, let's introduce a flag to indicate when that is precisely the logic we want.
We need a flag, and cannot rely on `is_repository_shallow()` to indicate that situation, because that function would return 0: There may not actually be a `shallow` file, as demonstrated e.g. by t5537.10 ("add new shallow root with receive.updateshallow on") and t5538.4 ("add new shallow root with receive.updateshallow on").
Note: shallow commits' parents are set to `NULL` internally already, therefore there is no need to special-case shallow repositories here, as the merge-base logic will not try to access parent commits of shallow commits.
Likewise, partial clones aren't an issue either: If a commit is missing during the revision walk in the merge-base logic, it is fetched via `promisor_remote_get_direct()`. And not only the single missing commit object: Due to the way the "promised" objects are fetched (in `fetch_objects()` in `promisor-remote.c`, using `fetch --filter=blob:none`), there is no actual way to fetch a single commit object, as the remote side will pass that commit OID to `pack-objects --revs [...]` which in turn passes it to `rev-list` which interprets this as a commit _range_ instead of a single object. Therefore, in partial clones (unless they are shallow in addition), all commits reachable from a commit that is in the local object database are also present in that local database.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> --- commit-reach.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/commit-reach.c b/commit-reach.c index 5ff71d72d51..7112b10eeea 100644 --- a/commit-reach.c +++ b/commit-reach.c @@ -53,7 +53,8 @@ static int queue_has_nonstale(struct prio_queue *queue) static struct commit_list *paint_down_to_common(struct repository *r, struct commit *one, int n, struct commit **twos, - timestamp_t min_generation) + timestamp_t min_generation, + int ignore_missing_commits) { struct prio_queue queue = { compare_commits_by_gen_then_commit_date }; struct commit_list *result = NULL; @@ -108,6 +109,13 @@ static struct commit_list *paint_down_to_common(struct repository *r, if (repo_parse_commit(r, p)) { clear_prio_queue(&queue); free_commit_list(result); + /* + * At this stage, we know that the commit is + * missing: `repo_parse_commit()` uses + * `OBJECT_INFO_DIE_IF_CORRUPT` and therefore + * corrupt commits would already have been + * dispatched with a `die()`. + */ return NULL; } p->object.flags |= flags; @@ -143,7 +151,7 @@ static struct commit_list *merge_bases_many(struct repository *r, return NULL; } - list = paint_down_to_common(r, one, n, twos, 0); + list = paint_down_to_common(r, one, n, twos, 0, 0); while (list) { struct commit *commit = pop_commit(&list); @@ -214,7 +222,7 @@ static int remove_redundant_no_gen(struct repository *r, min_generation = curr_generation; } common = paint_down_to_common(r, array[i], filled, - work, min_generation); + work, min_generation, 0); if (array[i]->object.flags & PARENT2) redundant[i] = 1; for (j = 0; j < filled; j++) @@ -504,7 +512,7 @@ int repo_in_merge_bases_many(struct repository *r, struct commit *commit, bases = paint_down_to_common(r, commit, nr_reference, reference, - generation); + generation, ignore_missing_commits); if (commit->object.flags & PARENT2) ret = 1; clear_commit_marks(commit, all_flags);
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