added universal node ownership

mods/universal_node_ownership/README.txt

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+[mod] Universal Node Ownership
+
+Forum Page: http://minetest.net/forum/viewtopic.php?pid=34814
+
+
+Contributors:
+mauvebic
+
+
+Description:
+
+Each node placed records its owner. Blocks placed by the server mapgen, or mods, are diggable. Nodes with owners can be removed using worldedit or multinode, or whatever tool mod that removes nodes instead of digging them.
+
+
+Installation:
+
+add to /buitin/builtin.lua, just below misc_register:
+dofile(minetest.get_modpath("__builtin").."/universal_node_ownership.lua")

mods/universal_node_ownership/universal_node_ownership.lua

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+-- add to /buitin/builtin.lua, just below misc_register:
+-- dofile(minetest.get_modpath("__builtin").."/universal_node_ownership.lua")
+
+local function is_node_owner(meta, player)
+    if meta:get_string("owner") ~= player:get_player_name() and meta:get_string("owner") ~= '' then
+        return false
+    end
+    return true
+end
+local can_dig = function(pos,player)
+    meta = minetest.env:get_meta(pos)
+    return is_node_owner(meta, player)
+end
+
+-- copy minetest.register_node to another function so we can still call it
+minetest_register_node = minetest.register_node;
+
+-- overwrite minetest.register_node
+function minetest.register_node(name, nodedef)
+    if not nodedef.can_dig then nodedef.can_dig = can_dig end
+    minetest_register_node(name, nodedef) -- call the real minetest.register_node
+end
+
+minetest.register_on_placenode(function(p, node, placer)
+    local meta = minetest.env:get_meta(p)
+    local player = placer:get_player_name()
+    meta:set_string("owner",player)
+end)