--- a/mercurial/node.py	Sat Mar 14 17:58:18 2015 +0900
+++ b/mercurial/node.py	Mon Jun 22 22:01:33 2015 +0900
@@ -10,6 +10,11 @@
 nullrev = -1
 nullid = "\0" * 20
 
+# pseudo identifiers for working directory
+# (they are experimental, so don't add too many dependencies on them)
+wdirrev = 0x7fffffff
+wdirid = "\xff" * 20
+
 # This ugly style has a noticeable effect in manifest parsing
 hex = binascii.hexlify
 bin = binascii.unhexlify