diff -r 38cf0908bf98 -r 5418dd5be8ac mercurial/bundlerepo.py
--- a/mercurial/bundlerepo.py	Thu Jun 25 17:42:45 2015 -0500
+++ b/mercurial/bundlerepo.py	Thu Jun 25 17:43:24 2015 -0500
@@ -346,6 +346,7 @@
 def instance(ui, path, create):
     if create:
         raise util.Abort(_('cannot create new bundle repository'))
+    # internal config: bundle.mainreporoot
     parentpath = ui.config("bundle", "mainreporoot", "")
     if not parentpath:
         # try to find the correct path to the working directory repo