--- a/mercurial/debugcommands.py	Sun Feb 12 03:06:38 2017 -0800
+++ b/mercurial/debugcommands.py	Wed Feb 01 17:48:30 2017 +0100
@@ -1414,6 +1414,27 @@
     ui.write('\n'.join(repo.pathto(p, cwd) for p in sorted(files)))
     ui.write('\n')
 
+@command('debugpushkey', [], _('REPO NAMESPACE [KEY OLD NEW]'), norepo=True)
+def debugpushkey(ui, repopath, namespace, *keyinfo, **opts):
+    '''access the pushkey key/value protocol
+
+    With two args, list the keys in the given namespace.
+
+    With five args, set a key to new if it currently is set to old.
+    Reports success or failure.
+    '''
+
+    target = hg.peer(ui, {}, repopath)
+    if keyinfo:
+        key, old, new = keyinfo
+        r = target.pushkey(namespace, key, old, new)
+        ui.status(str(r) + '\n')
+        return not r
+    else:
+        for k, v in sorted(target.listkeys(namespace).iteritems()):
+            ui.write("%s\t%s\n" % (k.encode('string-escape'),
+                                   v.encode('string-escape')))
+
 @command('debugupgraderepo', [
     ('o', 'optimize', [], _('extra optimization to perform'), _('NAME')),
     ('', 'run', False, _('performs an upgrade')),