git tag --contains: avoid stack overflow

In large repos, the recursion implementation of contains(commit,
commit_list) may result in a stack overflow. Replace the recursion with
a loop to fix it.

This problem is more apparent on Windows than on Linux, where the stack
is more limited by default.

See also this thread on the msysGit list:

	https://groups.google.com/d/topic/msysgit/FqT6boJrb2g/discussion

[jes: re-written to imitate the original recursion more closely]

Thomas Braun pointed out several documentation shortcomings.

Tests are run only if ulimit -s is available.  This means they cannot
be run on Windows.

Signed-off-by: Jean-Jacques Lafay <jeanjacques.lafay@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Tested-by: Stepan Kasal <kasal@ucw.cz>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index 143a8ea60..e4ab0f5b6 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -1423,4 +1423,30 @@ EOF
 	test_cmp expect actual
 '
 
+run_with_limited_stack () {
+	(ulimit -s 64 && "$@")
+}
+
+test_lazy_prereq ULIMIT 'run_with_limited_stack true'
+
+# we require ulimit, this excludes Windows
+test_expect_success ULIMIT '--contains works in a deep repo' '
+	>expect &&
+	i=1 &&
+	while test $i -lt 4000
+	do
+		echo "commit refs/heads/master
+committer A U Thor <author@example.com> $((1000000000 + $i * 100)) +0200
+data <<EOF
+commit #$i
+EOF"
+		test $i = 1 && echo "from refs/heads/master^0"
+		i=$(($i + 1))
+	done | git fast-import &&
+	git checkout master &&
+	git tag far-far-away HEAD^ &&
+	run_with_limited_stack git tag --contains HEAD >actual &&
+	test_cmp expect actual
+'
+
 test_done