workingfilectx: add exists, lexists

Switch the lone call in merge.py to use it.

As with past refactors, the goal is to make wctx hot-swappable with an
in-memory context in the future. This change should be a no-op today.

mercurial/context.py

@@ -1879,6 +1879,12 b' class workingfilectx(committablefilectx)'
                 raise
             return (t, tz)
 
+    def exists(self):
+        return self._repo.wvfs.exists(self._path)
+
+    def lexists(self):
+        return self._repo.wvfs.lexists(self._path)
+
     def audit(self):
         return self._repo.wvfs.audit(self._path)
 

mercurial/merge.py

@@ -9,7 +9,6 b' from __future__ import absolute_import'
 
 import errno
 import hashlib
-import os
 import shutil
 import struct
 
@@ -1206,7 +1205,7 b' def applyupdates(repo, actions, wctx, mc'
 
     # remove renamed files after safely stored
     for f in moves:
-        if os.path.lexists(repo.wjoin(f)):
+        if wctx[f].lexists():
             repo.ui.debug("removing %s\n" % f)
             wctx[f].audit()
             wctx[f].remove()