1 files changed, 45 insertions, 1 deletions
diff --git a/builtin/tag.c b/builtin/tag.c
index d311491e49..f7a7943c9d 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -12,6 +12,8 @@
 #include "tag.h"
 #include "run-command.h"
 #include "parse-options.h"
+#include "diff.h"
+#include "revision.h"
 
 static const char * const git_tag_usage[] = {
 	"git tag [-a|-s|-u <key-id>] [-f] [-m <msg>|-F <file>] <tagname> [<head>]",
@@ -31,6 +33,48 @@ struct tag_filter {
 
 #define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
 
+static int in_commit_list(const struct commit_list *want, struct commit *c)
+{
+	for (; want; want = want->next)
+		if (!hashcmp(want->item->object.sha1, c->object.sha1))
+			return 1;
+	return 0;
+}
+
+static int contains_recurse(struct commit *candidate,
+			    const struct commit_list *want)
+{
+	struct commit_list *p;
+
+	/* was it previously marked as containing a want commit? */
+	if (candidate->object.flags & TMP_MARK)
+		return 1;
+	/* or marked as not possibly containing a want commit? */
+	if (candidate->object.flags & UNINTERESTING)
+		return 0;
+	/* or are we it? */
+	if (in_commit_list(want, candidate))
+		return 1;
+
+	if (parse_commit(candidate) < 0)
+		return 0;
+
+	/* Otherwise recurse and mark ourselves for future traversals. */
+	for (p = candidate->parents; p; p = p->next) {
+		if (contains_recurse(p->item, want)) {
+			candidate->object.flags |= TMP_MARK;
+			return 1;
+		}
+	}
+	candidate->object.flags |= UNINTERESTING;
+	return 0;
+}
+
+static int contains(struct commit *candidate, const struct commit_list *want)
+{
+	return contains_recurse(candidate, want);
+}
+
 static int show_reference(const char *refname, const unsigned char *sha1,
 			  int flag, void *cb_data)
 {
@@ -49,7 +93,7 @@ static int show_reference(const char *refname, const unsigned char *sha1,
 			commit = lookup_commit_reference_gently(sha1, 1);
 			if (!commit)
 				return 0;
-			if (!is_descendant_of(commit, filter->with_commit))
+			if (!contains(commit, filter->with_commit))
 				return 0;
 		}