--- a/hgext/strip.py	Thu Sep 26 23:10:11 2013 +0200
+++ b/hgext/strip.py	Thu Sep 26 23:12:43 2013 +0200
@@ -1,5 +1,24 @@
-from mercurial import cmdutil
+from mercurial.i18n import _
+from mercurial import cmdutil, util
 
 cmdtable = {}
 command = cmdutil.command(cmdtable)
 testedwith = 'internal'
+
+def checksubstate(repo, baserev=None):
+    '''return list of subrepos at a different revision than substate.
+    Abort if any subrepos have uncommitted changes.'''
+    inclsubs = []
+    wctx = repo[None]
+    if baserev:
+        bctx = repo[baserev]
+    else:
+        bctx = wctx.parents()[0]
+    for s in sorted(wctx.substate):
+        if wctx.sub(s).dirty(True):
+            raise util.Abort(
+                _("uncommitted changes in subrepository %s") % s)
+        elif s not in bctx.substate or bctx.sub(s).dirty():
+            inclsubs.append(s)
+    return inclsubs
+