Fix the branding exploit

[mangband]

Issue raised by flambard

It is possible to generate unlimited amount of gold by buying base items, branding them and re-selling back to NPC shops.

There's nothing limiting this cycle, and it's known to be heavily used by cheesy players.

Possible solutions are: forbidding large stacks of weapons, or (if we ever get item origin implemented) making items bought from shop sell for less.

[mangband]

Comment by powerwyrm

I'll give you my solution: make items enchanted/branded by spells 100% off. I've done that for my variant, and it fixes the problem without much hassle.

[mangband]

Comment by flambard

I like PW's solution very much, but there's a corner use case:

Thorbear: the problem with solving this exploit is that a normal player, who doesn't exploit it, might want to sell his old dagger, which he enchanted to +9+9 once he finds an excellent weapon...

[mangband]

Comment by powerwyrm

As I said, the problem is real simple... make items enchanted/branded by spells 100% off. If you want to enchant an item and sell it afterwards, use scrolls.

[flambard-took]

If/when we port "object origin" flags from V ("that item was found on dungeon level 7"), we can simply only apply the 100%-off thing to items bought from shop/other players, and leave other items be.

[flambard-took]

We now do have item origins (see #1309), so I'm going to finally deal with this.