Fixed an exception in notify extension (b2a_hex argument incorrect)

Detailed messages was - incoming.notify hook raised an exception: b2a_hex() argument 1 must be string or read-only character buffer, not stringio

hgext/notify.py

@@ -238,7 +238,7 b' class notifier(object):'
             return
         fp = templater.stringio()
         prev = self.repo.changelog.parents(node)[0]
-        patch.diff(self.repo, fp, prev, ref)
+        patch.diff(self.repo, prev, ref, fp=fp)
         difflines = fp.getvalue().splitlines(1)
         if maxdiff > 0 and len(difflines) > maxdiff:
             self.sio.write(_('\ndiffs (truncated from %d to %d lines):\n\n') %