Standardize version update announcements

Announce to global chat on startup (for chat
bridges) and to each player on join, if the version
is different than the last time.

docs/ideas.txt

@@ -388,6 +388,8 @@ IDEAS: Possible future additions/improvements to the game
 	  that are saved in worlddir
 	- If mod is removed, items are replaced with their fallbacks
 	  by the game to avoid unknown_nodes.
+	- More complex items can register ingredients for "uncrafting"
+	  and automatic recycling; could work recursively.
 
 ........................................................................
 ========================================================================

mods/nc_api/init.lua

@@ -141,3 +141,5 @@ include("item_dig_destroy")
 
 include("item_groupdump")
 include("item_tiledump")
+
+include("setup_serverversion")

mods/nc_api/setup_serverversion.lua

@@ -0,0 +1,50 @@
+-- LUALOCALS < ---------------------------------------------------------
+local minetest, nodecore, os
+    = minetest, nodecore, os
+local os_time
+    = os.time
+-- LUALOCALS > ---------------------------------------------------------
+
+local modname = minetest.get_current_modname()
+local modstore = minetest.get_mod_storage()
+
+local updated = "NodeCore Updated: @1 -> @2"
+nodecore.translate_inform(updated)
+
+local verkey = modname .. "_version"
+local updkey = modname .. "_updated"
+
+local function vercomp(meta)
+	local newver = nodecore.version or "?"
+	local oldver = meta:get_string(verkey)
+	if oldver == "" then
+		meta:set_string(verkey, newver)
+		return
+	end
+	oldver = oldver ~= "" and oldver or "?"
+	if newver == oldver then return end
+	meta:set_string(verkey, newver)
+	meta:set_int(updkey, os_time())
+	return nodecore.translate(updated, oldver, newver)
+end
+
+-- Announce in public chat (for chat bridges)
+local function announce(depth)
+	if depth > 0 then
+		return minetest.after(0, function()
+				return announce(depth - 1)
+			end)
+	end
+	local text = vercomp(modstore)
+	if not text then return end
+	nodecore.log("warning", text)
+	return minetest.chat_send_all(text)
+end
+announce(5)
+
+-- Notify players on connect
+minetest.register_on_joinplayer(function(player)
+		local text = vercomp(player:get_meta())
+		if not text then return end
+		return minetest.chat_send_player(player:get_player_name(), text)
+	end)