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[PATCH] checkout: avoid BUG() when hitting a broken repository

From
Junio C Hamano <gitster@pobox.com>
Date
Jan 22, 2022, 00:58 UTC
Message-ID
<xmqqbl04d1s9.fsf_-_@gitster.g>
In-Reply-To
<xmqqlez8d2e6.fsf@gitster.g>
So, taking the two earlier comments from me together...

I _think_ I was the one who spotted the funny skip_prefix() whose result was not used, and suggested this unrelated check, during the review. Sorry about that.

----- >8 --------- >8 --------- >8 --------- >8 --------- >8 -----
Subject: [PATCH] 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>
---
 builtin/checkout.c         |  3 ---
 t/t2018-checkout-branch.sh | 13 +++++++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 43d0275187..1fb34d537d 100644
--- 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 93be1c0eae..5dda5ad4cb 100755
--- 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 &&
-- 
2.35.0-rc2-150-gc312dde8e9
Previous: Junio C HamanoNext: Johannes Sixt
Message 13 of 16 in “[BUG] builtin/checkout.c:1098: should be able to skip past 'refs/heads/'”
  1. Todd ZullingerJan 20, 2022
  2. Todd ZullingerJan 20, 2022
  3. checkout: fix BUG() case in 9081a421a6Ævar Arnfjörð Bjarmason, Jan 20, 2022
  4. Junio C HamanoJan 20, 2022
  5. Junio C HamanoJan 20, 2022
  6. Ævar Arnfjörð BjarmasonJan 21, 2022
  7. Petr ŠplíchalJan 21, 2022
  8. Todd ZullingerJan 21, 2022
  9. Junio C HamanoJan 21, 2022
  10. Todd ZullingerJan 20, 2022
  11. Junio C HamanoJan 22, 2022
  12. Junio C HamanoJan 22, 2022
  13. checkout: avoid BUG() when hitting a broken repositoryJunio C Hamano, Jan 22, 2022
  14. Johannes SixtJan 22, 2022
  15. Ævar Arnfjörð BjarmasonJan 22, 2022
  16. Johannes SchindelinJan 23, 2022

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