TSG S4: Avoid submerging Rangers

If no suitable forest hex is found, the radius of the locations considered is
extended instead of placing the unit next to Ethiliel.

Also, a change of behaviour:
 * non-free hexes will not be considered
 * the bodyguards won't be placed adjacent to other units, like the ambush
 ability works normally
 * this includes Ethiliel
In general that means that units may be placed farther away than before.

[ci skip]

(cherry-picked from commit e43b350)

data/campaigns/The_South_Guard/scenarios/04_Vale_of_Tears.cfg

@@ -436,79 +436,71 @@
             message= _ "You have a bodyguard?!"
         [/message]
 
-        [store_unit]
-            [filter]
-                id=Ethiliel
-            [/filter]
-            variable=ethiliel_loc
-            kill=no
-        [/store_unit]
-
-        [store_locations]
-            terrain=*^F*
-            [and]
-                x,y=$ethiliel_loc.x,$ethiliel_loc.y
-                radius=3
-            [/and]
-            variable=bodyguard_loc
-        [/store_locations]
-
-        {VARIABLE number 0}
-        [while]
-            [variable]
-                name=number
 #ifdef EASY
-                less_than=4
+        {VARIABLE hexes_needed 4}
 #endif
 #ifdef NORMAL
-                less_than=3
+        {VARIABLE hexes_needed 3}
 #endif
 #ifdef HARD
-                less_than=2
+        {VARIABLE hexes_needed 2}
 #endif
+
+        {VARIABLE extending 3}
+
+        # We assume that there are always at least $hexes_needed free
+        # forest hexes with no units adjacent on the whole map, otherwise
+        # this will be and endless loop.
+        [while]
+            [variable]
+                name=bodyguard_loc.length
+                less_than=$hexes_needed
             [/variable]
             [do]
-                # fallback coordinates, in case no nearby vacant forest is found
-                {VARIABLE guard_x $ethiliel_loc.x}
-                {VARIABLE guard_y $ethiliel_loc.y}
-
-                [if]
-                    [variable]
-                        name=number
-                        less_than=$bodyguard_loc.length
-                    [/variable]
-                    [then]
-                        [set_variable]
-                            name=guard_x
-                            value=$bodyguard_loc[$number].x
-                        [/set_variable]
-
-                        [set_variable]
-                            name=guard_y
-                            value=$bodyguard_loc[$number].y
-                        [/set_variable]
-                    [/then]
-                [/if]
+                [store_locations]
+                    terrain=*^F*
+                    [not]
+                        [filter]
+                            # only hexes where no unit is to be matched
+                        [/filter]
+                        radius=1 # nor adjacent, as with normal ambush ability
+                    [/not]
+                    [and]
+                        [filter]
+                            id=Ethiliel
+                        [/filter]
+                        radius=$extending
+                        include_borders=no
+                    [/and]
+                    variable=bodyguard_loc
+                    include_borders=no
+                [/store_locations]
+                {VARIABLE_OP extending add 1}
+            [/do]
+        [/while]
 
+        [for]
+            start=0
+            end=$($hexes_needed-1)
+            variable=i
+            [do]
                 [unit]
                     role=Elvish Bodyguard
                     name= _ "Elvish Bodyguard"
                     type=Elvish Ranger
                     side=1
-                    x,y=$guard_x,$guard_y
+                    x=$bodyguard_loc[$i].x
+                    y=$bodyguard_loc[$i].y
                     random_traits=yes
                     [modifications]
                         {TRAIT_LOYAL}
                     [/modifications]
                     {IS_LOYAL}
                 [/unit]
-
-                {VARIABLE_OP number add 1}
             [/do]
-        [/while]
+        [/for]
 
-        {CLEAR_VARIABLE bodyguard_loc,ethiliel_loc,number}
-        {CLEAR_VARIABLE guard_x,guard_y}
+        {CLEAR_VARIABLE bodyguard_loc,hexes_needed,extending}
 
         [message]
             role=Elvish Bodyguard