Increase contam from unequipping an item that's granting you invis (S…

…iegurt)

Technically it was still optimal to unequip invis items and then reequip them
to limit the time spent resting off contam. This change makes it always a bad
idea. It also adds a warning message when you try to take this action.

crawl-ref/source/invent.cc

@@ -1672,6 +1672,11 @@ bool needs_handle_warning(const item_def &item, operation_types oper,
         return true;
     }
 
+    // If you're invis from an item, warn that you're about to get an extra dose
+    // of contam from removing it.
+    if (you.duration[DUR_INVIS] > 1 && !you.attribute[ATTR_INVIS_UNCANCELLABLE])
+        return true;
+
     return false;
 }
 

crawl-ref/source/player-equip.cc

@@ -281,7 +281,12 @@ static void _unequip_invis()
         && !you.evokable_invis()
         && !you.attribute[ATTR_INVIS_UNCANCELLABLE])
     {
-        const int invis_duration_left = you.duration[DUR_INVIS];
+
+        // scale up contam by 120% just to ensure that ending invis early is
+        // worse than just resting it off.
+        mpr("You absorb a burst of magical contamination as your invisibility "
+             "abruptly ends!");
+        const int invis_duration_left = you.duration[DUR_INVIS] * 120 / 100;
         const int remaining_contam = div_rand_round(
             invis_duration_left * INVIS_CONTAM_PER_TURN, BASELINE_DELAY
         );