bag of tricks, horn of plenty, #tip (trunk only)

<Someone> reported that he applied an unID'd bag and it became
discovered as a bag of tricks even though a spellbook appeared on the floor
next to him rather than having a monster show up (the monster was a mimic).
Suppress the bag discovery unless you can see or sense a monster appear.
(This doesn't really achieve much for most players, who'll recognize the
bag because they know that only one type of container doesn't prompt to
take things out and/or put things in, but I think it does make sense.)

     While mucking with bag of tricks I decided that to be consistent with
the behavior of other containers, the #tip command should release all the
monsters in the bag instead of just one.

     And after doing that, I realized that horn of plenty ought to behave
much the same, so #tip will operate on it now.  However, it won't be listed
as a likely candidate in the "which item?" prompt unless/until it has been
discovered.  (Attempting to empty any other type of horn yields "nothing
happens", same as for a horn of plenty with no charges left.)  Emptying a
horn of plenty in a shop can be extremely verbose, but I don't think that
qualifies as a bug and don't currently have any plans to alter it.

src/invent.c

@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)invent.c	3.5	2006/05/17	*/
+/*	SCCS Id: @(#)invent.c	3.5	2006/06/17	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -896,7 +896,10 @@ register const char *let,*word;
 		      (otmp->dknown && objects[OIL_LAMP].oc_name_known))))
 		|| (!strcmp(word, "untrap with") &&
 		    (otmp->oclass == TOOL_CLASS && otyp != CAN_OF_GREASE))
-		|| (!strcmp(word, "tip") && !Is_container(otmp))
+		|| (!strcmp(word, "tip") && !Is_container(otmp) &&
+		   /* include horn of plenty if sufficiently discovered */
+		    (otmp->otyp != HORN_OF_PLENTY || !otmp->dknown ||
+			!objects[HORN_OF_PLENTY].oc_name_known))
 		|| (!strcmp(word, "charge") && !is_chargeable(otmp))
 		    )
 			foo--;