Add fix/tile-occupancy

Fixes bad unit/building occupancy flags

fix/tile-occupancy.lua

@@ -0,0 +1,56 @@
+-- Fix occupancy flags at a given tile
+
+--[====[
+
+fix/tile-occupancy
+==================
+Clears bad occupancy flags at the selected tile. Useful for getting rid of
+phantom "building present" messages. Currently only supports issues with
+building and unit occupancy. Requires that a tile is selected with the in-game
+cursor (``k``).
+
+Can be used to fix problematic tiles caused by :issue:`1047`.
+
+]====]
+
+if #{...} > 0 then
+    qerror('This script takes no arguments.')
+end
+
+function findUnit(x, y, z)
+    for _, u in pairs(df.global.world.units.active) do
+        if u.pos.x == x and u.pos.y == y and u.pos.z == z then
+            return true
+        end
+    end
+    return false
+end
+
+cursor = df.global.cursor
+changed = false
+function report(flag)
+    print('Cleared occupancy flag: ' .. flag)
+    changed = true
+end
+
+if cursor.x == -30000 then
+    qerror('Cursor not active.')
+end
+
+occ = dfhack.maps.getTileBlock(pos2xyz(cursor)).occupancy[cursor.x % 16][cursor.y % 16]
+
+if occ.building ~= 0 and not dfhack.buildings.findAtTile(pos2xyz(cursor)) then
+    occ.building = 0
+    report('building')
+end
+
+for _, flag in pairs{'unit', 'unit_grounded'} do
+    if occ[flag] and not findUnit(pos2xyz(cursor)) then
+        occ[flag] = false
+        report(flag)
+    end
+end
+
+if not changed then
+    print('No changes made at this tile.')
+end