Merge branch 'nd/attr-pathspec-in-tree-walk'

The traversal over tree objects has learned to honor
":(attr:label)" pathspec match, which has been implemented only for
enumerating paths on the filesystem.

* nd/attr-pathspec-in-tree-walk:
  tree-walk: support :(attr) matching
  dir.c: move, rename and export match_attrs()
  pathspec.h: clean up "extern" in function declarations
  tree-walk.c: make tree_entry_interesting() take an index
  tree.c: make read_tree*() take 'struct repository *'

builtin/grep.c

@@ -553,7 +553,8 @@ static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
 
 		if (match != all_entries_interesting) {
 			strbuf_addstr(&name, base->buf + tn_len);
-			match = tree_entry_interesting(&entry, &name,
+			match = tree_entry_interesting(repo->index,
+						       &entry, &name,
 						       0, pathspec);
 			strbuf_setlen(&name, name_base_len);