tree-diff: drop list-tail argument to diff_tree_paths()

The internals of the path diffing code, including ll_diff_tree_paths(),
all take an extra combine_diff_path parameter which they use as the tail
of a list of results, appending any new entries to it.

The public-facing diff_tree_paths() takes the same argument, but it just
makes the callers more awkward. They always start with a clean list, and
have to set up a fake head struct to pass in.

Let's keep the public API clean by always returning a new list. That
keeps the fake struct as an implementation detail of tree-diff.c.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 6 deletions

diff --git a/combine-diff.c b/combine-diff.c
index f21e1f58ba..9527f3160d 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -1428,22 +1428,19 @@ static struct combine_diff_path *find_paths_multitree(
 {
 	int i, nparent = parents->nr;
 	const struct object_id **parents_oid;
-	struct combine_diff_path paths_head;
+	struct combine_diff_path *paths;
 	struct strbuf base;
 
 	ALLOC_ARRAY(parents_oid, nparent);
 	for (i = 0; i < nparent; i++)
 		parents_oid[i] = &parents->oid[i];
 
-	/* fake list head, so worker can assume it is non-NULL */
-	paths_head.next = NULL;
-
 	strbuf_init(&base, PATH_MAX);
-	diff_tree_paths(&paths_head, oid, parents_oid, nparent, &base, opt);
+	paths = diff_tree_paths(oid, parents_oid, nparent, &base, opt);
 
 	strbuf_release(&base);
 	free(parents_oid);
-	return paths_head.next;
+	return paths;
 }
 
 static int match_objfind(struct combine_diff_path *path,