Fix a regression in my 9081a421a6d (checkout: fix "branch info" memory leaks, 2021-11-16) where I'd assumed that the old_branch_info.path would have to start with refs/heads/*, but as has been reported[1] that's not the case. As a test case[2] to reproduce this shows the second "git checkout" here runs into the BUG() in the pre-image. The test being added is amended from[2] and will pass both with this change, and before 9081a421a6. I.e. our behavior now is again the same as before that commit. 1. https://bugzilla.redhat.com/show_bug.cgi?id=2042920 2. https://lore.kernel.org/git/YemTGQZ97vAPUPY0@xxxxxxxxx/ Reported-by: Petr Šplíchal <psplicha@xxxxxxxxxx> Reported-by: Todd Zullinger <tmz@xxxxxxxxx> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> --- On Thu, Jan 20 2022, Todd Zullinger wrote: > Hi, > > A bug was filed in the Fedora/Red Hat bugzilla today for the > git 2.35.0 rc (rc1, but it's the same in rc2). Petr (Cc'd), > ran the following > > git clone https://github.com/psss/fmf /tmp/fmf > cd /tmp/fmf > cp .git/refs/remotes/origin/HEAD .git/refs/heads/__DEFAULT__ > git checkout -f __DEFAULT__ > git checkout -f __DEFAULT__ > > The second git checkout call runs into the BUG() call added > in 9081a421a6 (checkout: fix "branch info" memory leaks, > 2021-11-16): > > BUG: builtin/checkout.c:1098: should be able to skip > past 'refs/heads/' in 'refs/remotes/origin/master'! > Aborted (core dumped) > > This worked in 2.34.1, so it's new to 2.35.0. Should this > work or does the manual copy to setup a branch fall into a > new category of "don't do that"? > > (It's novel to get a bug report from rc testing of a distro > build -- that doesn't happen often.) Thanks to both you and Petr for the report and easy to reproduce case, and sorry about causing it. In retrospec it's a rather obvious thinko. Here's a minimal fix for it, along with a derived test case that I made more exhaustive to check the state of the repo before, after, and in-between the two "git checkout" commands. As noted it'll also pass with 9081a421a6d reverted, showing that our behavior is the same as before that commit. builtin/checkout.c | 11 ++++------- t/t2018-checkout-branch.sh | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+), 7 deletions(-) diff --git a/builtin/checkout.c b/builtin/checkout.c index 6a5dd2a2a22..52a47ef40e1 100644 --- a/builtin/checkout.c +++ b/builtin/checkout.c @@ -1090,13 +1090,10 @@ static int switch_branches(const struct checkout_opts *opts, FREE_AND_NULL(old_branch_info.path); if (old_branch_info.path) { - const char *const prefix = "refs/heads/"; - const char *p; - if (skip_prefix(old_branch_info.path, prefix, &p)) - old_branch_info.name = xstrdup(p); - else - BUG("should be able to skip past '%s' in '%s'!", - prefix, old_branch_info.path); + const char *p = old_branch_info.path; + + skip_prefix(old_branch_info.path, "refs/heads/", &p); + old_branch_info.name = xstrdup(p); } if (opts->new_orphan_branch && opts->orphan_from_empty_tree) { diff --git a/t/t2018-checkout-branch.sh b/t/t2018-checkout-branch.sh index 3e93506c045..82df9b8bf64 100755 --- a/t/t2018-checkout-branch.sh +++ b/t/t2018-checkout-branch.sh @@ -85,6 +85,39 @@ test_expect_success 'setup' ' git branch -m branch1 ' +test_expect_success REFFILES 'checkout a branch without refs/heads/* prefix' ' + git clone --no-tags . repo-odd-prefix && + ( + cd repo-odd-prefix && + + cp .git/refs/remotes/origin/HEAD .git/refs/heads/a-branch && + + echo branch1 >expect.ref && + git rev-parse --abbrev-ref HEAD >actual.ref && + test_cmp expect.ref actual.ref && + + git checkout -f a-branch && + + echo origin/branch1 >expect.ref && + git rev-parse --abbrev-ref HEAD >actual.ref && + test_cmp expect.ref actual.ref && + + git checkout -f a-branch && + + cat >expect <<-EOF && + $(git rev-parse HEAD) commit refs/heads/a-branch + $(git rev-parse HEAD) commit refs/heads/branch1 + $(git rev-parse HEAD) commit refs/remotes/origin/HEAD + $(git rev-parse HEAD) commit refs/remotes/origin/branch1 + EOF + git for-each-ref >actual && + test_cmp expect actual && + + git rev-parse --abbrev-ref HEAD >actual && + test_cmp expect.ref actual.ref + ) +' + test_expect_success 'checkout -b to a new branch, set to HEAD' ' test_when_finished " git checkout branch1 && -- 2.35.0.rc1.864.g57621b115b6
