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[PATCH] Revert "reflog expire: don't use lookup_commit_reference_gently()"

From
Junio C Hamano <gitster@pobox.com>
Date
Jul 16, 2024, 19:56 UTC
Message-ID
<xmqqv8156rh2.fsf@gitster.g>

During Git 2.35 timeframe, daf1d828 (reflog expire: don't use lookup_commit_reference_gently(), 2021-12-22) replaced a call to lookup_commit_reference_gently() with a call to lookup_commit().

What it failed to consider was that our refs do not necessarily point at commits (most notably, we have annotated and signed tags), and more importantly that lookup_commit() does not dereference a tag to return a commit; instead it returns NULL when a tag is given.

Since the commit returned is used as a starting point for the reachability check, this ejected the commits that are reachable only by an annotated tag out of the set of reachable commits, breaking the computation to correctly implement the "--expire-unreachable" option. We also started giving an error message that the API function expected to be fed a commit object.

This problem hasn't been reported or noticed for a long time, probably because the "refs/tags/" hierarchy by default is not covered by reflogs, as nobody usually moves tags.

Revert the change to correctly find the commit pointed at by the ref to restore the previous behaviour, but do so only in a more modern codebase, as we had significant code churn since then and it is not grave enough to worry about for older maintenance tracks.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
  cf. <patch-v3-6.9-cfa80e84c6d-20211222T040557Z-avarab@gmail.com>
 reflog.c          | 3 ++-
 t/t1410-reflog.sh | 8 ++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/reflog.c b/reflog.c
index 0a1bc35e8c..2e45a17e12 100644
--- a/reflog.c
+++ b/reflog.c
@@ -330,7 +330,8 @@ void reflog_expiry_prepare(const char *refname,
 	if (!cb->cmd.expire_unreachable || is_head(refname)) {
 		cb->unreachable_expire_kind = UE_HEAD;
 	} else {
-		commit = lookup_commit(the_repository, oid);
+		commit = lookup_commit_reference_gently(the_repository,
+							oid, 1);
 		if (commit && is_null_oid(&commit->object.oid))
 			commit = NULL;
 		cb->unreachable_expire_kind = commit ? UE_NORMAL : UE_ALWAYS;
diff --git a/t/t1410-reflog.sh b/t/t1410-reflog.sh
index d2f5f42e67..16816e82b2 100755
--- a/t/t1410-reflog.sh
+++ b/t/t1410-reflog.sh
@@ -146,6 +146,14 @@ test_expect_success rewind '
 	test_line_count = 5 output
 '
 
+test_expect_success 'reflog expire should not barf on an annotated tag' '
+	test_when_finished "git tag -d v0.tag || :" &&
+	git -c core.logAllRefUpdates=always \
+		tag -a -m "tag name" v0.tag main &&
+	git reflog expire --dry-run refs/tags/v0.tag 2>err &&
+	test_grep ! "error: [Oo]bject .* not a commit" err
+'
+
 test_expect_success 'corrupt and check' '
 
 	corrupt $F &&
-- 
2.46.0-rc0-153-ge537c69d48
Next: Jeff King
Message 1 of 3 in “Revert "reflog expire: don't use lookup_commit_reference_gently()"”
  1. Revert "reflog expire: don't use lookup_commit_reference_gently()"Junio C Hamano, Jul 16, 2024
  2. Jeff KingJul 17, 2024
  3. Junio C HamanoJul 17, 2024

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