filelog: stop proxying deltaparent() (API) deltaparent() obtains the revision number of the base revision a delta in storage is stored against. It is highly revlog-centric and may not apply to other storage backends. As a result, it doesn't belong on the generic file storage interface. This method/proxy is no longer used in core. The last consumer was probably changegroup code and went away with the transition to emitrevisions(). Differential Revision: https://phab.mercurial-scm.org/D4751

--- a/mercurial/repository.py	Mon Sep 24 12:49:17 2018 -0700
+++ b/mercurial/repository.py	Mon Sep 24 13:35:50 2018 -0700
@@ -533,9 +533,6 @@
         Returns a list of nodes.
         """
 
-    def deltaparent(rev):
-        """"Return the revision that is a suitable parent to delta against."""
-
 class ifiledata(interfaceutil.Interface):
     """Storage interface for data storage of a specific file.