diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -13,6 +13,7 @@ from mercurial import mdiff
 
 def hex(node): return binascii.hexlify(node)
 def bin(node): return binascii.unhexlify(node)
+def short(node): return hex(node[:4])
 
 def compress(text):
     return zlib.compress(text)