unionrepo: sync with repository API

unionrepo: sync with repository API

Differential Revision: https://phab.mercurial-scm.org/D6289

--- a/mercurial/unionrepo.py	Tue Apr 23 08:39:26 2019 -0700
+++ b/mercurial/unionrepo.py	Fri Apr 19 20:06:37 2019 +0200
@@ -128,9 +128,10 @@
 
     def addrevision(self, text, transaction, link, p1=None, p2=None, d=None):
         raise NotImplementedError
-    def addgroup(self, deltas, transaction, addrevisioncb=None):
+    def addgroup(self, deltas, linkmapper, transaction, addrevisioncb=None,
+                 maybemissingparents=False):
         raise NotImplementedError
-    def strip(self, rev, minlink):
+    def strip(self, minlink, transaction):
         raise NotImplementedError
     def checksize(self):
         raise NotImplementedError