context: drop caching 'copies' method

The 'copies' method has no test coverage and calls copies.pathcopies with an
incorrect number of parameters and is thus (fortunately) not used. Kill it.

mercurial/context.py

@@ -8,7 +8,6 b''
 from node import nullid, nullrev, short, hex, bin
 from i18n import _
 import ancestor, mdiff, error, util, scmutil, subrepo, patch, encoding, phases
-import copies
 import match as matchmod
 import os, errno, stat
 import obsolete as obsmod
@@ -737,14 +736,6 b' class basefilectx(object):'
             c = visit.pop(max(visit))
             yield c
 
-    def copies(self, c2):
-        if not util.safehasattr(self, "_copycache"):
-            self._copycache = {}
-        sc2 = str(c2)
-        if sc2 not in self._copycache:
-            self._copycache[sc2] = copies.pathcopies(c2)
-        return self._copycache[sc2]
-
 class filectx(basefilectx):
     """A filecontext object makes access to data related to a particular
        filerevision convenient."""