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.

mercurial/context.py

@@ -340,7 +340,7 b' class basectx(object):'
 
 
 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 b' def makememctx(repo, parents, text, user'
         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,