[PATCH 02 of 14 RFC] context: add a method to convert node to ctx

[Sean Farley]

# HG changeset patch
# User Sean Farley <sean.michael.farley at gmail.com>
# Date 1373322965 18000
#      Mon Jul 08 17:36:05 2013 -0500
# Node ID bf0f87c072f524b8e054de72af143a0dfc2fcffb
# Parent  2bda9c94e65cff8c6968d82cfc07ec6049b194c0
context: add a method to convert node to ctx

I had a hard time deciding where to place this function. Perhaps it could go
into scmutil or util?

This adds a method as a common place for testing if an object is a context
object, and if it isn't, then to find the corresponding context object in the
repo.

diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -14,10 +14,15 @@
 import obsolete as obsmod
 import repoview
 
 propertycache = util.propertycache
 
+def nodeorctx(repo, node):
+    if isinstance(node, changectx):
+        return node
+    return repo[node]
+
 class changectx(object):
     """A changecontext object makes access to data related to a particular
     changeset convenient."""
     def __init__(self, repo, changeid=''):
         """changeid is a revision number, node, or tag"""