checkout: pass the "num_matches" up to callers

Pass the previously added "num_matches" struct value up to the callers
of unique_tracking_name(). This will allow callers to optionally print
better error messages in a later change.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/worktree.c b/builtin/worktree.c
index 5c7d2bb..a763dbd 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -412,7 +412,7 @@ static const char *dwim_branch(const char *path, const char **new_branch)
 	if (guess_remote) {
 		struct object_id oid;
 		const char *remote =
-			unique_tracking_name(*new_branch, &oid);
+			unique_tracking_name(*new_branch, &oid, NULL);
 		return remote;
 	}
 	return NULL;
@@ -484,7 +484,7 @@ static int add(int ac, const char **av, const char *prefix)
 
 		commit = lookup_commit_reference_by_name(branch);
 		if (!commit) {
-			remote = unique_tracking_name(branch, &oid);
+			remote = unique_tracking_name(branch, &oid, NULL);
 			if (remote) {
 				new_branch = branch;
 				branch = remote;