Revert "Default repo manifest settings in git config"

This reverts commit ee1c2f5717fcc137ab887a4aae8a08d50a539b9a.

This breaks a lot of buildbot systems. Rolling it back for now
until we can understand what the breakage was and how to fix it.
diff --git a/repo b/repo
index 0b20a9b..2a13af5 100755
--- a/repo
+++ b/repo
@@ -28,7 +28,7 @@
 del magic
 
 # increment this whenever we make important changes to this script
-VERSION = (1, 14)
+VERSION = (1, 13)
 
 # increment this if the MAINTAINER_KEYS block is modified
 KEYRING_VERSION = (1,0)
@@ -154,7 +154,7 @@
   """Installs repo by cloning it over the network.
   """
   opt, args = init_optparse.parse_args(args)
-  if args:
+  if args or not opt.manifest_url:
     init_optparse.print_usage()
     sys.exit(1)