checkout: avoid BUG() when hitting a broken repository

When 9081a421 (checkout: fix "branch info" memory leaks, 2021-11-16)
cleaned up existing memory leaks, we added an unrelated sanity check
to ensure that a local branch is truly local and not a symref to
elsewhere that dies with BUG() otherwise.  This was misguided in two
ways.  First of all, such a tightening did not belong to a leak-fix
patch.  And the condition it detected was *not* a bug in our program
but a problem in user data, where warning() or die() would have been
more appropriate.

As the condition is not fatal (the result of computing the local
branch name in the code that is involved in the faulty check is only
used as a textual label for the commit), let's revert the code to
the original state, i.e. strip "refs/heads/" to compute the local
branch name if possible, and otherwise leave it NULL.  The consumer
of the information in merge_working_tree() is prepared to see NULL
in there and act accordingly.

cf. https://bugzilla.redhat.com/show_bug.cgi?id=2042920

Reported-by: Petr Šplíchal <psplicha@redhat.com>
Reported-by: Todd Zullinger <tmz@pobox.com>
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 43d0275187fc8fcac9f7106fb511b08f527b488e..1fb34d537d9e915fabf310725cea2d23af2735fd 100644 (file)
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1094,9 +1094,6 @@ static int switch_branches(const struct checkout_opts *opts,
                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);
        }
 
        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 93be1c0eae5ead7eeb4f37dab01dbc1c1fbacdba..5dda5ad4cbcb078ad8536f9b7437be640473aa77 100755 (executable)
--- a/t/t2018-checkout-branch.sh
+++ b/t/t2018-checkout-branch.sh
@@ -85,6 +85,19 @@ test_expect_success 'setup' '
        git branch -m branch1
 '
 
+test_expect_success 'checkout a branch without refs/heads/* prefix' '
+       git clone --no-tags . repo-odd-prefix &&
+       (
+               cd repo-odd-prefix &&
+
+               origin=$(git symbolic-ref refs/remotes/origin/HEAD) &&
+               git symbolic-ref refs/heads/a-branch "$origin" &&
+
+               git checkout -f a-branch &&
+               git checkout -f a-branch
+       )
+'
+
 test_expect_success 'checkout -b to a new branch, set to HEAD' '
        test_when_finished "
                git checkout branch1 &&