debugger: give a little intro before entering pdb

mercurial/dispatch.py

@@ -49,6 +49,8 b' def _runcatch(ui, args):'
         try:
             # enter the debugger before command execution
             if '--debugger' in args:
+                ui.warn(_("entering debugger - "
+                        "type c to continue starting hg or h for help\n"))
                 pdb.set_trace()
             try:
                 return _dispatch(ui, args)