patch: add 'extra' argument to makememctx

patch: add 'extra' argument to makememctx

The uncommit command in evolve needs to create memory context with given
extra parameters. This patch allows us to do that instead of always giving them
an empty value and having to override it afterwards.

--- a/mercurial/context.py	Wed May 27 17:41:42 2015 -0500
+++ b/mercurial/context.py	Fri May 22 13:06:45 2015 -0700
@@ -340,7 +340,7 @@
 
 
 def makememctx(repo, parents, text, user, date, branch, files, store,
-               editor=None):
+               editor=None, extra=None):
     def getfilectx(repo, memctx, path):
         data, mode, copied = store.getfile(path)
         if data is None:
@@ -348,7 +348,8 @@
         islink, isexec = mode
         return memfilectx(repo, path, data, islink=islink, isexec=isexec,
                                   copied=copied, memctx=memctx)
-    extra = {}
+    if extra is None:
+        extra = {}
     if branch:
         extra['branch'] = encoding.fromlocal(branch)
     ctx =  memctx(repo, parents, text, files, getfilectx, user,