remote prune: optimize "dangling symref" check/warning

When 'git remote prune' was used to delete many refs in a repository
with many refs, a lot of time was spent checking for (now) dangling
symbolic refs pointing to the deleted ref, since warn_dangling_symref()
was once per deleted ref to check all other refs in the repository.

Avoid this using the new warn_dangling_symrefs() function which
makes one pass over all refs and checks for all the deleted refs in
one go, after they have all been deleted.

Signed-off-by: Jens Lindström <jl@opera.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/refs.c b/refs.c
index 262c1c26c..59fb70087 100644
--- a/refs.c
+++ b/refs.c
@@ -1611,6 +1611,7 @@ int peel_ref(const char *refname, unsigned char *sha1)
 struct warn_if_dangling_data {
 	FILE *fp;
 	const char *refname;
+	const struct string_list *refnames;
 	const char *msg_fmt;
 };
 
@@ -1625,8 +1626,12 @@ static int warn_if_dangling_symref(const char *refname, const unsigned char *sha
 		return 0;
 
 	resolves_to = resolve_ref_unsafe(refname, junk, 0, NULL);
-	if (!resolves_to || strcmp(resolves_to, d->refname))
+	if (!resolves_to
+	    || (d->refname
+		? strcmp(resolves_to, d->refname)
+		: !string_list_has_string(d->refnames, resolves_to))) {
 		return 0;
+	}
 
 	fprintf(d->fp, d->msg_fmt, refname);
 	fputc('\n', d->fp);
@@ -1639,6 +1644,18 @@ void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
 
 	data.fp = fp;
 	data.refname = refname;
+	data.refnames = NULL;
+	data.msg_fmt = msg_fmt;
+	for_each_rawref(warn_if_dangling_symref, &data);
+}
+
+void warn_dangling_symrefs(FILE *fp, const char *msg_fmt, const struct string_list *refnames)
+{
+	struct warn_if_dangling_data data;
+
+	data.fp = fp;
+	data.refname = NULL;
+	data.refnames = refnames;
 	data.msg_fmt = msg_fmt;
 	for_each_rawref(warn_if_dangling_symref, &data);
 }