Make monster pathfinding less player-centric

Most pathfinding checks assumed that the only thing a monster
would be trying to path towards was the player, even though this
was frequently untrue (either hostile monsters targeting player allies
or friendly monsters trying to reach other monsters). A few bugs
existed as a result of this:

When monsters without ranged attacks would check the reachability of
their foe, they would check the reachability of the player instead,
regardless of what was shooting at them or whether the player was
even involved in the battle. This meant that melee-only monsters
would flee from ranged attacks in the arena (where the player is
understandably never reachable) and also could show up occasionally in
normal play - such as retreating from an oklob fort if the player
is behind water.

I expect there are a few other bugs related to similar assumptions,
but moreover, allowing monsters to use proper pathfinding to non-player
foes likely improves ally intelligence somewhat.

As always with fiddly monster behavioral code, there is a non-trivial
chance that some important side-effect has been overlooked, but initial
testing looks good.

1 files changed, 1 insertions, 1 deletions

diff --git a/crawl-ref/source/misc.cc b/crawl-ref/source/misc.cc
index 550cedec55..298d95cfd5 100644
--- a/crawl-ref/source/misc.cc
+++ b/crawl-ref/source/misc.cc
@@ -1414,7 +1414,7 @@ static bool _mons_has_path_to_player(const monster* mon, bool want_move = false)
 
     // If the monster is awake and knows a path towards the player
     // (even though the player cannot know this) treat it as unsafe.
-    if (mon->travel_target == MTRAV_PLAYER)
+    if (mon->travel_target == MTRAV_FOE)
         return true;
 
     if (mon->travel_target == MTRAV_KNOWN_UNREACHABLE)