Maintain selection directionality when merging selections with keyboard

src/atom/composite-selection.coffee

@@ -49,11 +49,11 @@ class CompositeSeleciton
 
   selectLeft: ->
     selection.selectLeft() for selection in @getSelections()
-    @mergeIntersectingSelections()
+    @mergeIntersectingSelections reverse: true
 
   selectUp: ->
     selection.selectUp() for selection in @getSelections()
-    @mergeIntersectingSelections()
+    @mergeIntersectingSelections reverse: true
 
   selectDown: ->
     selection.selectDown() for selection in @getSelections()
@@ -71,14 +71,14 @@ class CompositeSeleciton
   lastSelection: ->
     _.last(@selections)
 
-  mergeIntersectingSelections: ->
+  mergeIntersectingSelections: (options) ->
     for selection in @getSelections()
       otherSelections = @getSelections()
       _.remove(otherSelections, selection)
       for otherSelection in otherSelections
         if selection.intersectsWith(otherSelection)
-          selection.merge(otherSelection)
-          @mergeIntersectingSelections()
+          selection.merge(otherSelection, options)
+          @mergeIntersectingSelections(options)
           return
 
   modifySelectedText: (fn) ->

src/atom/selection.coffee

@@ -139,11 +139,14 @@ class Selection extends View
   isEmpty: ->
     @getBufferRange().isEmpty()
 
+  isReversed: ->
+    @cursor.getBufferPosition().isLessThan(@anchorBufferPosition)
+
   intersectsWith: (otherSelection) ->
     @getScreenRange().intersectsWith(otherSelection.getScreenRange())
 
-  merge: (otherSelection) ->
-    @setScreenRange(@getScreenRange().union(otherSelection.getScreenRange()))
+  merge: (otherSelection, options) ->
+    @setScreenRange(@getScreenRange().union(otherSelection.getScreenRange()), options)
     otherSelection.remove()
 
   remove: ->