gitc: Improve help visibility

This improves the visiblity of gitc-init if we can get the gitc config,
and hides it otherwise.

Change-Id: I82830b0b07c311e8c74397ba79eb4c361f8b6fb5

command.py

@@ -230,3 +230,8 @@ class MirrorSafeCommand(object):
   """Command permits itself to run within a mirror,
      and does not require a working directory.
   """
+
+class RequiresGitcCommand(object):
+  """Command that requires GITC to be available, but does
+     not require the local client to be a GITC client.
+  """