Unbreak Thorn Hunter bunkering behavior

It is a somewhat alarming sign of how brittle it might be that it
managed to stop working across just the commits in this branch,
and the 'solution' feels like major hack to me as well.

Fixing general monster pathfinding around briar patches meant that
thorn hunters would no longer bother to fire through them, but
instead simply walk around. Now pathfinding opacity is special-cased
so that thorn hunters will consider briar patches transparent (and
thus attempt to move into them, triggering their firing behavior).

If someone can think of a better way to implement this, I'm all ears.

1 files changed, 10 insertions, 1 deletions

diff --git a/crawl-ref/source/mon-pathfind.cc b/crawl-ref/source/mon-pathfind.cc
index 02aecc2b86..f3c2b88e75 100644
--- a/crawl-ref/source/mon-pathfind.cc
+++ b/crawl-ref/source/mon-pathfind.cc
@@ -415,7 +415,16 @@ bool monster_pathfind::traversable(const coord_def& p)
     if (opc_immob(p) == OPC_OPAQUE
         && grd(p) != DNGN_CLOSED_DOOR && grd(p) != DNGN_SEALED_DOOR)
     {
-        return false;
+        // XXX: Ugly hack to make thorn hunters use their briars for defensive
+        //      cover instead of just pathing around them.
+        if (mons->type == MONS_THORN_HUNTER
+            && monster_at(p)
+            && monster_at(p)->type == MONS_BRIAR_PATCH)
+        {
+            return true;
+        }
+        else
+            return false;
     }
 
     if (mons)