Make rev-list --objects work together with pathspecs

When traversing commits, the selection of commits would heed the list of
pathspecs passed, but subsequent walking of the trees of those commits
would not.  This resulted in 'rev-list --objects HEAD -- <paths>'
displaying objects at unwanted paths.

Have process_tree() call tree_entry_interesting() to determine which paths
are interesting and should be walked.

Naturally, this change can provide a large speedup when paths are specified
together with --objects, since many tree entries are now correctly ignored.
Interestingly, though, this change also gives me a small (~1%) but
repeatable speedup even when no paths are specified with --objects.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

list-objects.c

@@ -61,12 +61,15 @@ static void process_tree(struct rev_info *revs,
 			 struct tree *tree,
 			 show_object_fn show,
 			 struct name_path *path,
+			 struct strbuf *base,
 			 const char *name)
 {
 	struct object *obj = &tree->object;
 	struct tree_desc desc;
 	struct name_entry entry;
 	struct name_path me;
+	int all_interesting = (revs->diffopt.pathspec.nr == 0);
+	int baselen = base->len;
 
 	if (!revs->tree_objects)
 		return;
@@ -82,13 +85,32 @@ static void process_tree(struct rev_info *revs,
 	me.elem = name;
 	me.elem_len = strlen(name);
 
+	if (!all_interesting) {
+		strbuf_addstr(base, name);
+		if (base->len)
+			strbuf_addch(base, '/');
+	}
+
 	init_tree_desc(&desc, tree->buffer, tree->size);
 
 	while (tree_entry(&desc, &entry)) {
+		if (!all_interesting) {
+			int showit = tree_entry_interesting(&entry,
+							    base, 0,
+							    &revs->diffopt.pathspec);
+
+			if (showit < 0)
+				break;
+			else if (!showit)
+				continue;
+			else if (showit == 2)
+				all_interesting = 1;
+		}
+
 		if (S_ISDIR(entry.mode))
 			process_tree(revs,
 				     lookup_tree(entry.sha1),
-				     show, &me, entry.path);
+				     show, &me, base, entry.path);
 		else if (S_ISGITLINK(entry.mode))
 			process_gitlink(revs, entry.sha1,
 					show, &me, entry.path);
@@ -97,6 +119,7 @@ static void process_tree(struct rev_info *revs,
 				     lookup_blob(entry.sha1),
 				     show, &me, entry.path);
 	}
+	strbuf_setlen(base, baselen);
 	free(tree->buffer);
 	tree->buffer = NULL;
 }
@@ -146,7 +169,9 @@ void traverse_commit_list(struct rev_info *revs,
 {
 	int i;
 	struct commit *commit;
+	struct strbuf base;
 
+	strbuf_init(&base, PATH_MAX);
 	while ((commit = get_revision(revs)) != NULL) {
 		add_pending_tree(revs, commit->tree);
 		show_commit(commit, data);
@@ -164,7 +189,7 @@ void traverse_commit_list(struct rev_info *revs,
 		}
 		if (obj->type == OBJ_TREE) {
 			process_tree(revs, (struct tree *)obj, show_object,
-				     NULL, name);
+				     NULL, &base, name);
 			continue;
 		}
 		if (obj->type == OBJ_BLOB) {
@@ -181,4 +206,5 @@ void traverse_commit_list(struct rev_info *revs,
 		revs->pending.alloc = 0;
 		revs->pending.objects = NULL;
 	}
+	strbuf_release(&base);
 }