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

subcmds/help.py

@@ -19,7 +19,8 @@ import sys
 from formatter import AbstractFormatter, DumbWriter
 
 from color import Coloring
-from command import PagedCommand, MirrorSafeCommand
+from command import PagedCommand, MirrorSafeCommand, RequiresGitcCommand
+import gitc_utils
 
 class Help(PagedCommand, MirrorSafeCommand):
   common = False
@@ -54,9 +55,17 @@ Displays detailed usage information about a command.
   def _PrintCommonCommands(self):
     print('usage: repo COMMAND [ARGS]')
     print('The most commonly used repo commands are:')
+
+    def gitc_supported(cmd):
+      if not isinstance(cmd, RequiresGitcCommand):
+        return True
+      if gitc_utils.get_gitc_manifest_dir():
+        return True
+      return False
+
     commandNames = list(sorted([name
                     for name, command in self.commands.items()
-                    if command.common]))
+                    if command.common and gitc_supported(command)]))
 
     maxlen = 0
     for name in commandNames: