cloner to easily clone dependent repositories

The intent is to replace the devstack shell script with a python utility
which would be easy to reuse.

Change-Id: I3c8748e2544af80e72fdd0b2e3627b4fc2212c01
diff --git a/setup.cfg b/setup.cfg
index 21b1199..a4deb2f 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -24,6 +24,7 @@
     zuul-server = zuul.cmd.server:main
     zuul-merger = zuul.cmd.merger:main
     zuul = zuul.cmd.client:main
+    zuul-cloner = zuul.cmd.cloner:main
 
 [build_sphinx]
 source-dir = doc/source