Merge branch 'kn/attr-from-tree'

"git check-attr" learned to take an optional tree-ish to read the
.gitattributes file from.

* kn/attr-from-tree:
  attr: add flag `--source` to work with tree-ish
  t0003: move setup for `--all` into new block

pathspec.c

@@ -730,7 +730,7 @@ int match_pathspec_attrs(struct index_state *istate,
 	if (name[namelen])
 		name = to_free = xmemdupz(name, namelen);
 
-	git_check_attr(istate, name, item->attr_check);
+	git_check_attr(istate, NULL, name, item->attr_check);
 
 	free(to_free);