Clarify options that control the repo executable version

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/subcmds/init.py b/subcmds/init.py
index 103a78d..3a5c766 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -64,7 +64,7 @@
 
 
     # Tool
-    g = p.add_option_group('Version options')
+    g = p.add_option_group('repo Version options')
     g.add_option('--repo-url',
                  dest='repo_url',
                  help='repo repository location', metavar='URL')