Add GitcClientCommand class for GITC-specific commands

These won't show up as common commands in the help text unless in a GITC
client, and will refuse to execute.

Change-Id: Iffe82adcc9d6ddde9cb4b204f83ff018042bdab0

main.py

@@ -42,7 +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 command import GitcAvailableCommand, GitcClientCommand
 from subcmds.version import Version
 from editor import Editor
 from error import DownloadError
@@ -144,11 +144,16 @@ class _Repo(object):
             file=sys.stderr)
       return 1
 
-    if isinstance(cmd, RequiresGitcCommand) and not gitc_utils.get_gitc_manifest_dir():
+    if isinstance(cmd, GitcAvailableCommand) and not gitc_utils.get_gitc_manifest_dir():
       print("fatal: '%s' requires GITC to be available" % name,
             file=sys.stderr)
       return 1
 
+    if isinstance(cmd, GitcClientCommand) and not gitc_client_name:
+      print("fatal: '%s' requires a GITC client" % name,
+            file=sys.stderr)
+      return 1
+
     try:
       copts, cargs = cmd.OptionParser.parse_args(argv)
       copts = cmd.ReadEnvironmentOptions(copts)