Updating comments in BasePolygonBuilder to explain "pairwise" intersection

src/main/java/org/elasticsearch/common/geo/builders/BasePolygonBuilder.java

@@ -395,7 +395,15 @@ public abstract class BasePolygonBuilder<E extends BasePolygonBuilder<E>> extend
                 holes[e2.component-1] = holes[numHoles];
                 holes[numHoles] = null;
             }
-            // only connect edges if intersections are pairwise (per comment above)
+            // only connect edges if intersections are pairwise 
+            // per the comment above, the edge array is sorted by y-value of the intersection
+            // with the dateline.  Two edges have the same y intercept when they cross the 
+            // dateline thus they appear sequentially (pairwise) in the edge array. Two edges
+            // do not have the same y intercept when we're forming a multi-poly from a poly
+            // that wraps the dateline (but there are 2 ordered intercepts).  
+            // The connect method creates a new edge for these paired edges in the linked list. 
+            // For boundary conditions (e.g., intersect but not crossing) there is no sibling edge 
+            // to connect. Thus the following enforces the pairwise rule 
             if (e1.intersect != Edge.MAX_COORDINATE && e2.intersect != Edge.MAX_COORDINATE) {
                 connect(e1, e2);
             }