store: sort the results of fncachestore.datafiles()

mercurial/store.py

@@ -398,7 +398,7 b' class fncachestore(basicstore):'
     def datafiles(self):
         rewrite = False
         existing = []
-        for f in self.fncache:
+        for f in sorted(self.fncache):
             ef = self.encode(f)
             try:
                 yield f, ef, self.getsize(ef)