mercurial/commands.py

--- a/mercurial/commands.py	Wed Nov 11 13:28:00 2015 -0800
+++ b/mercurial/commands.py	Tue Nov 17 14:22:30 2015 -0800
@@ -2556,6 +2556,9 @@
                 ui.write(('unrecognized entry: %s\t%s\n')
                          % (rtype, record.replace('\0', '\t')))
 
+    # Avoid mergestate.read() since it may raise an exception for unsupported
+    # merge state records. We shouldn't be doing this, but this is OK since this
+    # command is pretty low-level.
     ms = mergemod.mergestate(repo)
 
     # sort so that reasonable information is on top