[PATCH v2 12/16] refs/packed-backend.c: ignore complicated hidden refs rules

[Taylor Blau <me@ttaylorr.com>]

In subsequent commits, we'll teach `receive-pack` and `upload-pack` to
use the new skip-list feature in the packed-refs iterator by ignoring
references which are mentioned via its respective hideRefs lists.

However, the packed-ref skip lists cannot handle un-hiding rules (that
begin with '!'), or namespace comparisons (that begin with '^'). Detect
and avoid these cases by falling back to the normal enumeration without
a skip list when such patterns exist.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 refs/packed-backend.c   | 19 +++++++++++++++++++
 t/t1419-exclude-refs.sh |  9 +++++++++
 2 files changed, 28 insertions(+)

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index 7ba9fa2bb8..9ea6c07866 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -1015,6 +1015,25 @@ static void populate_excluded_jump_list(struct packed_ref_iterator *iter,
 	if (!excluded_patterns)
 		return;
 
+	for (pattern = excluded_patterns; *pattern; pattern++) {
+		/*
+		 * We also can't feed any excludes from hidden refs
+		 * config sections, since later rules may override
+		 * previous ones. For example, with rules "refs/foo" and
+		 * "!refs/foo/bar", we should show "refs/foo/bar" (and
+		 * everything underneath it), but the earlier exclusion
+		 * would cause us to skip all of "refs/foo". We likewise
+		 * don't implement the namespace stripping required for
+		 * '^' rules.
+		 *
+		 * Both are possible to do, but complicated, so avoid
+		 * populating the jump list at all if we see either of
+		 * these patterns.
+		 */
+		if (**pattern == '!' || **pattern == '^')
+			return;
+	}
+
 	for (pattern = excluded_patterns; *pattern; pattern++) {
 		struct jump_list_entry *e;
 
diff --git a/t/t1419-exclude-refs.sh b/t/t1419-exclude-refs.sh
index 350a7d2587..0e91e2f399 100755
--- a/t/t1419-exclude-refs.sh
+++ b/t/t1419-exclude-refs.sh
@@ -119,4 +119,13 @@ test_expect_success 'meta-characters are discarded' '
 	assert_no_jumps
 '
 
+test_expect_success 'complex hidden ref rules are discarded' '
+	for_each_ref__exclude refs/heads refs/heads/foo "!refs/heads/foo/1" \
+		>actual 2>perf &&
+	for_each_ref >expect &&
+
+	test_cmp expect actual &&
+	assert_no_jumps
+'
+
 test_done
-- 
2.40.1.572.g5c4ab523ef