Merge branch 'nd/add-empty-fix'

"git add -A" (no other arguments) in a totally empty working tree
used to emit an error.

* nd/add-empty-fix:
  add: don't complain when adding empty project root

builtin/add.c

@@ -547,7 +547,7 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 			const char *path = pathspec.items[i].match;
 			if (pathspec.items[i].magic & PATHSPEC_EXCLUDE)
 				continue;
-			if (!seen[i] &&
+			if (!seen[i] && path[0] &&
 			    ((pathspec.items[i].magic &
 			      (PATHSPEC_GLOB | PATHSPEC_ICASE)) ||
 			     !file_exists(path))) {