From: Harald Nordgren via GitGitGadget Date: Wed, 24 Jun 2026 21:54:56 GMT Subject: [PATCH v15 0/2] checkout: --track=fetch Message-ID: In-Reply-To: Extend checkout --track with a fetch mode to refresh start-point. Changes in v15: * Reword commit message to lead with motivation. * Drop RESOLVE_REF_NO_RECURSE so /HEAD lookup matches what git checkout does for the same ref. Drop redundant check_refname_format on a ref we just read. Replace memset with brace initializer. Use refs_ref_exists and pass NULL for the OID out-params. * Split the "set HEAD" error onto its own line via die_message and advise, matching the suggested format. * Remove 6 redundant tests, replace test $a = $b with test_cmp_rev, and rename test titles to avoid "namespace". Changes in v14: * Handle .h files in a better way. Changes in v13: * Create a preparatory commit that exposes find_tracking_remote_for_ref() and advise_ambiguous_fetch_refspec() from branch.c, so checkout can reuse the same lookup git branch --track uses. * Use advise_ambiguous_fetch_refspec() for the "multiple remotes match" case, so the wording matches git branch --track. Harald Nordgren (2): branch: expose helpers for finding the remote owning a tracking ref checkout: extend --track with a "fetch" mode to refresh start-point Documentation/git-checkout.adoc | 17 ++- Documentation/git-switch.adoc | 5 +- branch.c | 96 +++++++------- branch.h | 16 +++ builtin/checkout.c | 138 +++++++++++++++++++- t/t7201-co.sh | 222 ++++++++++++++++++++++++++++++++ 6 files changed, 443 insertions(+), 51 deletions(-) base-commit: ab776a62a78576513ee121424adb19597fbb7613 Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v15 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v15 Pull-Request: https://github.com/git/git/pull/2281 Range-diff vs v14: 1: f79689c23d = 1: 8139490c36 branch: expose helpers for finding the remote owning a tracking ref 2: 8518f090b1 ! 2: b7e387f123 checkout: extend --track with a "fetch" mode to refresh start-point @@ Metadata ## Commit message ## checkout: extend --track with a "fetch" mode to refresh start-point - Add a "fetch" mode to the "--track" option of "git checkout" / "git - switch" that refreshes before checking it out: + Forking from an existing remote branch without refreshing first often + has consequences: you start work that has already been done, or you + build on an old version of the code which causes big conflicts later + when you pull. The workaround is two commands ("git fetch + && git checkout -b /"), and when + the fetch is skipped the checkout silently starts from a stale tip. - git checkout -b new_branch --track=fetch origin/some-branch + Users may already expect "/" to refer to the latest + tip on the remote. While this blurs the line between fetch and + checkout, git already does this in places where it pays off: "git + clone" fetches and checks out, and "git pull" fetches and merges. - is shorthand for + Add a "fetch" mode to "--track" that refreshes before + checking it out: - git fetch origin some-branch - git checkout -b new_branch --track origin/some-branch + git checkout -b new_branch --track=fetch origin/some-branch - Identify the remote whose configured fetch refspec maps to - using find_tracking_remote_for_ref() (the same lookup - "--track" uses to pick which remote to record in - branch..remote), then run "git fetch " for - just that ref so other remote-tracking branches are left untouched. - When is a bare (e.g. "origin"), follow - refs/remotes//HEAD to learn which branch to refresh. If - "git fetch" fails but the remote-tracking ref already exists locally, - warn and proceed from the existing tip; otherwise abort. + Only the requested branch is fetched so other remote-tracking + branches are left untouched. When is a bare + (e.g. "origin"), follow refs/remotes//HEAD to learn which + branch to refresh. If "git fetch" fails but the remote-tracking ref + already exists locally, warn and proceed from the existing tip, + otherwise abort. Signed-off-by: Harald Nordgren @@ builtin/checkout.c: struct branch_info { +static void fetch_remote_for_start_point(const char *arg, int quiet) +{ + struct strbuf dst = STRBUF_INIT; -+ struct tracking tracking; ++ struct tracking tracking = { 0 }; + struct string_list tracking_srcs = STRING_LIST_INIT_DUP; + struct string_list ambiguous_remotes = STRING_LIST_INIT_DUP; + struct child_process cmd = CHILD_PROCESS_INIT; -+ struct object_id oid; + struct remote *named_remote; + int bare_ns; + @@ builtin/checkout.c: struct branch_info { + const char *head_target = + refs_resolve_ref_unsafe(get_main_ref_store(the_repository), + head_path, -+ RESOLVE_REF_READING | -+ RESOLVE_REF_NO_RECURSE, -+ &oid, NULL); ++ RESOLVE_REF_READING, ++ NULL, NULL); + if (head_target && + starts_with(head_target, dst.buf) && -+ head_target[dst.len] == '/' && -+ !check_refname_format(head_target, 0)) { ++ head_target[dst.len] == '/') { + strbuf_reset(&dst); + strbuf_addstr(&dst, head_target); + bare_ns = 0; @@ builtin/checkout.c: struct branch_info { + free(head_path); + } + -+ memset(&tracking, 0, sizeof(tracking)); + tracking.spec.dst = dst.buf; + tracking.srcs = &tracking_srcs; + find_tracking_remote_for_ref(&tracking, &ambiguous_remotes); @@ builtin/checkout.c: struct branch_info { + + if (!tracking.matches) { + if (bare_ns && named_remote && -+ remote_is_configured(named_remote, 1)) -+ die(_("cannot fetch start-point '%s': " -+ "'refs/remotes/%s/HEAD' is not set; run " -+ "'git remote set-head %s --auto' to set it"), -+ arg, arg, arg); ++ remote_is_configured(named_remote, 1)) { ++ int status = die_message(_("cannot fetch start-point '%s' " ++ "because 'refs/remotes/%s/HEAD' " ++ "does not exist."), arg, arg); ++ advise(_("To create it run\n" ++ "\n" ++ " git remote set-head %s --auto\n"), arg); ++ exit(status); ++ } + die(_("cannot fetch start-point '%s': no configured remote's " + "fetch refspec matches it"), arg); + } @@ builtin/checkout.c: struct branch_info { + tracking_srcs.items[0].string, NULL); + cmd.git_cmd = 1; + if (run_command(&cmd)) { -+ if (!refs_read_ref(get_main_ref_store(the_repository), -+ dst.buf, &oid)) ++ if (refs_ref_exists(get_main_ref_store(the_repository), dst.buf)) + warning(_("failed to fetch start-point '%s'; " + "using existing '%s'"), arg, dst.buf); + else @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh + git -C fetch_upstream checkout -b fetch_other && + test_commit -C fetch_upstream u_other_pre && + git fetch fetch_upstream && -+ other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) && ++ git update-ref refs/heads/snapshot_other refs/remotes/fetch_upstream/fetch_other && + git -C fetch_upstream checkout fetch_target && + test_commit -C fetch_upstream u_target_post && + git -C fetch_upstream checkout fetch_other && + test_commit -C fetch_upstream u_other_post && + git checkout --track=fetch -b local_target fetch_upstream/fetch_target && + test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD && -+ test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before" ++ test_cmp_rev refs/remotes/fetch_upstream/fetch_other snapshot_other +' + +test_expect_success 'checkout --track=fetch with bare remote name fetches only /HEAD target' ' @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh + git -C fetch_upstream checkout -b fetch_unrelated && + test_commit -C fetch_upstream u_unrelated_pre && + git fetch fetch_upstream fetch_unrelated && -+ unrelated_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated) && ++ git update-ref refs/heads/snapshot_unrelated \ ++ refs/remotes/fetch_upstream/fetch_unrelated && + git -C fetch_upstream checkout main && + test_commit -C fetch_upstream u_main_post && + git -C fetch_upstream checkout fetch_unrelated && + test_commit -C fetch_upstream u_unrelated_post && + git checkout --track=fetch -b local_from_remote fetch_upstream && + test_cmp_rev refs/remotes/fetch_upstream/main HEAD && -+ test "$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated)" = "$unrelated_before" ++ test_cmp_rev refs/remotes/fetch_upstream/fetch_unrelated snapshot_unrelated +' + +test_expect_success 'checkout --track=fetch aborts and does not create branch when no existing ref' ' @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh + test_cmp_rev refs/remotes/custom-ns/fetch_refspec HEAD +' + -+test_expect_success 'checkout --track=fetch on namespace bare name follows /HEAD' ' ++test_expect_success 'checkout --track=fetch on bare remote-tracking prefix follows /HEAD' ' + git checkout main && + git remote add fetch_ns ./fetch_upstream && + test_when_finished "git remote remove fetch_ns" && @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh + test_cmp_config refs/heads/main branch.local_ns.merge +' + -+test_expect_success '--track=fetch on bare hierarchical remote name follows /HEAD' ' -+ git checkout main && -+ git remote add nested/bare ./fetch_upstream && -+ test_when_finished "git remote remove nested/bare" && -+ test_when_finished "git update-ref -d refs/remotes/nested/bare/HEAD" && -+ git fetch nested/bare && -+ git symbolic-ref refs/remotes/nested/bare/HEAD \ -+ refs/remotes/nested/bare/main && -+ git -C fetch_upstream checkout main && -+ test_commit -C fetch_upstream u_nested_bare_post && -+ git checkout --track=fetch -b local_nested_bare nested/bare && -+ test_cmp_rev refs/remotes/nested/bare/main HEAD -+' -+ -+test_expect_success 'checkout --track=fetch handles hierarchical remote name' ' -+ git checkout main && -+ git remote add nested/remote ./fetch_upstream && -+ test_when_finished "git remote remove nested/remote" && -+ git -C fetch_upstream checkout -b fetch_hier && -+ test_commit -C fetch_upstream u_hier && -+ test_must_fail git rev-parse --verify refs/remotes/nested/remote/fetch_hier && -+ git checkout --track=fetch -b local_hier nested/remote/fetch_hier && -+ test_cmp_rev refs/remotes/nested/remote/fetch_hier HEAD -+' -+ +test_expect_success 'checkout --track=fetch dies on bare remote name with no /HEAD' ' + git checkout main && + git remote add fetch_nohead ./fetch_upstream && @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh + test_must_fail git rev-parse --verify refs/heads/local_unknown +' + -+test_expect_success 'checkout --track=fetch rejects /HEAD pointing outside namespace' ' ++test_expect_success 'checkout --track=fetch rejects /HEAD pointing outside the tracking prefix' ' + git checkout main && + git remote add fetch_crossns ./fetch_upstream && + test_when_finished "git remote remove fetch_crossns" && @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh + test_must_fail git rev-parse --verify refs/heads/local_invalid +' + -+test_expect_success 'checkout --track=fetch,inherit rejects invalid refname components' ' -+ git checkout main && -+ test_must_fail git checkout --track=fetch,inherit -b local_invalid \ -+ "foo..bar" 2>err && -+ test_grep "valid" err && -+ test_must_fail git rev-parse --verify refs/heads/local_invalid -+' -+ +test_expect_success 'checkout --track=inherit,direct is rejected' ' + test_must_fail git checkout --track=inherit,direct -b bad fetch_upstream/fetch_new 2>err && + test_grep "cannot combine" err +' + -+test_expect_success 'checkout --track=direct,inherit is rejected' ' -+ test_must_fail git checkout --track=direct,inherit -b bad fetch_upstream/fetch_new 2>err && -+ test_grep "cannot combine" err -+' -+ +test_expect_success 'checkout --track=fetch then --track=direct drops fetch (last-one-wins)' ' + git checkout main && + git -C fetch_upstream checkout -b fetch_lastwin && @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh + test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin +' + -+test_expect_success 'checkout --track=fetch then --no-track drops fetch' ' -+ git checkout main && -+ git -C fetch_upstream checkout -b fetch_notrack && -+ test_commit -C fetch_upstream u_notrack && -+ test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_notrack && -+ test_must_fail git checkout --track=fetch --no-track \ -+ -b local_notrack fetch_upstream/fetch_notrack && -+ test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_notrack -+' -+ +test_expect_success 'checkout --track=fetch,inherit fetches remote-tracking start-point' ' + git checkout main && + git -C fetch_upstream checkout -b fetch_inherit && @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh + test_cmp_rev refs/remotes/fetch_upstream/fetch_inherit HEAD +' + -+test_expect_success 'checkout --track=fetch,inherit errors when start-point does not map to a remote' ' -+ git checkout main && -+ test_must_fail git checkout --track=fetch,inherit -b bad main 2>err && -+ test_grep "no configured remote" err && -+ test_must_fail git rev-parse --verify refs/heads/bad -+' -+ +test_expect_success 'checkout --track=fetch on local start-point errors' ' + git checkout main && + test_must_fail git checkout --track=fetch -b bad main 2>err && -- gitgitgadget