Add on_grant and on_revoke callbacks

[rubenwardy]

minetest.register_privilege("test", {
	on_grant = function(name, grantername)
		local gname = grantername or "<?>"
		print(gname .. " granted " .. name .. " test")
	end,
	on_revoke = function(name, revokername)
		local rname = revokername or "<?>"
		print(rname .. " revoked " .. name .. " test")
	end,
})

The second commit makes it work with mods generally, however the callbacks are called twice when doing /grant - once for when doing set_privs, the other from the /grant function.

USE CASES

• Allows you to implement hud flag privileges, eg: minimap priv, without polling for priv changes
• Update Unified Inventory main buttons on priv changes
• ...

TODO

• Documentation

[Wuzzy2]

Add “Update Unified Inventory main buttons” to the list of use cases. :-)

I like the concept (I am generally in favor of new callbacks) and say “Thank you!”.

[rubenwardy]

Currently callbacks being called twice, once with the player name and once without. I don't think it's that bad, and it's hard to fix cleanly. Alternatively, I could do on_player_grant etc and then it would call each callback at most once.

[nerzhul]

dup code, please factorize

[nerzhul]

please fix dup code and reduce code indent with functions and i'm okay

[SmallJoker]

Unusual long line. Mind moving more to the second one?

[SmallJoker]

Tested, works. You've got some debugging leftovers, which also need to be removed before merge.

[rubenwardy]

updated. I think I'm going to split the callback in two - on_grant and on_granted_by_player. This makes the behaviour seem less odd, imo.

[nerzhul]

Okay for me