diff -r ae04af1ce78d -r dc9fb7015d7f mercurial/commands.py
--- a/mercurial/commands.py	Sun Nov 13 00:29:26 2011 +0000
+++ b/mercurial/commands.py	Sat Nov 12 13:15:40 2011 +0100
@@ -2590,7 +2590,10 @@
             cont = False
 
         # commit
-        extra = {'source': ctx.hex()}
+        source = ctx.extra().get('source')
+        if not source:
+            source = ctx.hex()
+        extra = {'source': source}
         user = ctx.user()
         if opts.get('user'):
             user = opts['user']