remove extension commands from global help

mercurial/commands.py

@@ -1310,6 +1310,8 b' def help_(ui, name=None, with_version=Fa'
             f = c.split("|", 1)[0]
             if select and not select(f):
                 continue
+            if select is None and e[0].__module__ != __name__:
+                continue
             if name == "shortlist" and not f.startswith("^"):
                 continue
             f = f.lstrip("^")