Track can-dig check: also notify user when digging is not allowed

advtrains/locale/advtrains.de.tr

@@ -66,6 +66,7 @@ Subway Passenger Wagon=U-Bahn-Waggon
 The wagon's inventory is not empty!=Das Inventar dieses Waggons ist nicht leer!
 This track can not be changed!=Diese Schiene kann nicht geändert werden!
 This track can not be rotated!=Diese Schiene kann nicht gedreht werden!
+This track can not be removed!=Diese Schiene kann nicht entfernt werden!
 Position is occupied by a train.=Ein Zug steht an dieser Position.
 There's a Track Circuit Break here.=Hier ist eine Gleisabschnittsgrenze (TCB).
 There's a Signal Influence Point here.=Hier ist ein Signal-Beeinflussungspunkt.

advtrains/tracks.lua

@@ -442,6 +442,15 @@ Depending on the number of connections:
 	- conn3 <> conn4
 ]]
 
+-- Notify the user if digging the rail is not allowed
+local function can_dig_callback(pos, player)
+	local ok, reason = advtrains.can_dig_or_modify_track(pos)
+	if not ok and player then
+		minetest.chat_send_player(player:get_player_name(), attrans("This track can not be removed!") .. " " .. reason)
+	end
+	return ok
+end
+
 function advtrains.register_tracks(tracktype, def, preset)
 	advtrains.trackplacer.register_tracktype(def.nodename_prefix, preset.tpdefault)
 	if preset.regtp then
@@ -478,7 +487,7 @@ function advtrains.register_tracks(tracktype, def, preset)
 						not_blocking_trains=1,
 					},
 						
-					can_dig = advtrains.can_dig_or_modify_track,
+					can_dig = can_dig_callback,
 					after_dig_node=function(pos)
 						advtrains.ndb.update(pos)
 					end,