Hide debug commands in ambiguous command list, unless no normal command matches.

This will execute diff if 'hg d' is typed and hide rawcommit on 'hg r'.
Based on a patch by TK Soh.

mercurial/commands.py

@@ -2679,15 +2679,22 b' norepo = ("clone init version help debug'
 def find(cmd):
     """Return (aliases, command table entry) for command string."""
     choice = []
+    debugchoice = []
     for e in table.keys():
         aliases = e.lstrip("^").split("|")
         if cmd in aliases:
             return aliases, table[e]
         for a in aliases:
             if a.startswith(cmd):
-                choice.append([aliases, table[e]])
+                if aliases[0].startswith("debug"):
+                    debugchoice.append([aliases, table[e]])
+                else:
+                    choice.append([aliases, table[e]])
                 break
 
+    if not choice and debugchoice:
+        choice = debugchoice
+
     if len(choice) > 1:
         clist = []
         for aliases, table_e in choice: