match: define exactmatcher.matchfn statically
This should eliminate the reference cycle, self.matchfn -> self.exact -> self.
--- a/mercurial/match.py Sun May 28 23:51:30 2017 +0900
+++ b/mercurial/match.py Sun May 28 23:54:31 2017 +0900
@@ -415,7 +415,8 @@
self._files = files
else:
self._files = list(files)
- self.matchfn = self.exact
+
+ matchfn = basematcher.exact
@propertycache
def _dirs(self):