mercurial/match.py

--- a/mercurial/match.py	Mon Aug 08 22:06:07 2016 -0700
+++ b/mercurial/match.py	Tue Aug 09 09:02:51 2016 +0000
@@ -320,6 +320,10 @@
             kindpats.append((kind, pat, ''))
         return kindpats
 
+    def matchessubrepo(self, subpath):
+        return (self.exact(subpath)
+                or any(f.startswith(subpath + '/') for f in self.files()))
+
 def exact(root, cwd, files, badfn=None):
     return match(root, cwd, files, exact=True, badfn=badfn)