Merge branch 'jk/diff-highlight-blank-match-fix'

"diff-highlight" (in contrib/) had a logic to flush its output upon
seeing a blank line but the way it detected a blank line was broken.

* jk/diff-highlight-blank-match-fix:
  diff-highlight: correctly match blank lines for flush

contrib/diff-highlight/DiffHighlight.pm

@@ -112,7 +112,7 @@ sub handle_line {
 	# Since we can receive arbitrary input, there's no optimal
 	# place to flush. Flushing on a blank line is a heuristic that
 	# happens to match git-log output.
-	if (!length) {
+	if (/^$/) {
 		$flush_cb->();
 	}
 }