--- a/mercurial/cmdutil.py	Wed Nov 02 18:56:07 2016 +0000
+++ b/mercurial/cmdutil.py	Wed Nov 02 18:45:53 2016 +0000
@@ -3403,6 +3403,14 @@
 
     return cmd
 
+def checkunresolved(ms):
+    if list(ms.unresolved()):
+        raise error.Abort(_("unresolved merge conflicts "
+                            "(see 'hg help resolve')"))
+    if ms.mdstate() != 's' or list(ms.driverresolved()):
+        raise error.Abort(_('driver-resolved merge conflicts'),
+                          hint=_('run "hg resolve --all" to resolve'))
+
 # a list of (ui, repo, otherpeer, opts, missing) functions called by
 # commands.outgoing.  "missing" is "missing" of the result of
 # "findcommonoutgoing()"