Merge pull request DFHack#5578 from SilasD/zone-trader-critters

Prevent assignment of trader-owned small pets (items, not units) to pits, ponds, and cages.

Author: ab9rf

docs/changelog.txt

@@ -56,6 +56,7 @@ Template for new versions:
 ## New Features
 
 ## Fixes
+- small animals owned by traders can no longer be assigned to pits, ponds, and cages.
 
 ## Misc Improvements
 

plugins/lua/zone.lua

@@ -602,7 +602,9 @@ local function is_assignable_unit(unit)
 end
 
 local function is_assignable_item(item)
-    -- all vermin/small pets are assignable
+    -- small pets owned by traders are not assignable
+    if item.flags.trader then return false end
+    -- other vermin/small pets are assignable
     return true
 end