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

main.py

@@ -42,6 +42,7 @@ from git_command import git, GitCommand
 from git_config import init_ssh, close_ssh
 from command import InteractiveCommand
 from command import MirrorSafeCommand
+from command import RequiresGitcCommand
 from subcmds.version import Version
 from editor import Editor
 from error import DownloadError
@@ -143,6 +144,11 @@ class _Repo(object):
             file=sys.stderr)
       return 1
 
+    if isinstance(cmd, RequiresGitcCommand) and not gitc_utils.get_gitc_manifest_dir():
+      print("fatal: '%s' requires GITC to be available" % name,
+            file=sys.stderr)
+      return 1
+
     try:
       copts, cargs = cmd.OptionParser.parse_args(argv)
       copts = cmd.ReadEnvironmentOptions(copts)