Default repo manifest settings in git config

A default manifest URL can be specified using:
  git config --global repo-manifest.<id>.url <url>

A default manifest server can be specified using:
  git config --global repo-manifest.<id>.server <url>

A default git mirror reference can be specified using:
  git config --global repo-manifest.<id>.reference <path>

This will allow the user to use 'repo init -u <id>' as
a shorter alternative to specifying the full URL.

Also, manifest server will not have to be specified in the
manifest XML and the reference will not have to be specified
on the command line. If they are, they will override these
default values however.

Change-Id: Ifdbc160bd5909ec7df9efb0c5d7136f1d9351754
Signed-off-by: Victor Boivie <victor.boivie@sonyericsson.com>
diff --git a/repo b/repo
index 0e77983..1c71f07 100755
--- a/repo
+++ b/repo
@@ -28,7 +28,7 @@
 del magic
 
 # increment this whenever we make important changes to this script
-VERSION = (1, 13)
+VERSION = (1, 14)
 
 # increment this if the MAINTAINER_KEYS block is modified
 KEYRING_VERSION = (1,0)
@@ -149,7 +149,7 @@
   """Installs repo by cloning it over the network.
   """
   opt, args = init_optparse.parse_args(args)
-  if args or not opt.manifest_url:
+  if args:
     init_optparse.print_usage()
     sys.exit(1)