Guidebook update: "Shops"

Add a new section about shops to the Guidebook.  I don't think any
significant spoilers are revealed.

doc/Guidebook.mn

@@ -5,7 +5,7 @@
 .ds vr "NetHack 3.4
 .ds f0 "\*(vr
 .ds f1
-.ds f2 "November 15, 2003
+.ds f2 "November 25, 2003
 .mt
 A Guide to the Mazes of Menace
 (Guidebook for NetHack)
@@ -877,6 +877,50 @@ Ladders (`<', `>')
 .pg
 Ladders serve the same purpose as staircases, and the two types of
 inter-level connections are nearly indistinguishable during game play.
+.hn 2
+Shops and shopping
+.pg
+Occasionally you will run across a room with a shopkeeper near the door
+and many items laying on the floor.  You can buy items by picking them
+up and then using the `p' command.  You can inquire about the price
+of an item prior to picking it up by using the ``#chat'' command
+while standing on it.  Using an item prior to paying for it will incur a
+charge, and the shopkeeper won't allow you to leave the shop until you
+have paid any debt you owe.
+.pg
+You can sell items to a shopkeeper by dropping them to the floor while
+inside a shop.  You will either be offered an amount of gold and asked
+whether you're willing to sell, or you'll be told that the shopkeeper
+isn't interested (generally, your item needs to be compatible with the
+type of merchandize carried by the shop).
+.pg
+If you drop something in a shop by accident, the shopkeeper will usually
+claim ownership without offering any compensation.  You'll have to buy
+it back if you want to reclaim it.
+.pg
+Shopkeepers sometimes run out of money.  When that happens, you'll be
+offered credit instead of gold when you try to sell something.  Credit
+can be used to pay for purchases, but it is only good in the shop where
+it was obtained; other shopkeepers won't honor it.  (If you happen to
+find a "credit card" in the dungeon, don't bother trying to use it in
+shops; shopkeepers will not accept it.)
+.hn 3
+Shop idiosyncracies
+.pg
+Several aspects of shop behavior might be unexpected.
+.\" note: using * instead of \(bu is better for plain text output
+.lp * 2
+The price of a given item can vary due to a variety of factors.
+.lp * 2
+A shopkeeper treats the spot immediately inside the door as if it were
+outside the shop.
+.lp * 2
+While the shopkeeper watches you like a hawk, he will generally ignore
+any other customers.
+.lp * 2
+If a shop is "closed for inventory", it will not open of its own accord.
+.lp * 2
+Shops do not get restocked with new items, regardless of inventory depletion.
 
 .hn 1
 Monsters