Autoscroll the last cursor when it inserts text

Normally, we don't autoscroll to a cursor when the buffer changes. But
this is a change caused by the cursor itself, so it makes sense to
keep it in view.

spec/app/editor-spec.coffee

@@ -1155,6 +1155,15 @@ describe "Editor", ->
           editor.setCursorBufferPosition([4, 10])
           expect(editor.scrollToPixelPosition).toHaveBeenCalled()
 
+        it "does not autoscroll the cursor based on a buffer change, unless the buffer change was initiated by the cursor", ->
+          lastVisibleRow = editor.getLastVisibleScreenRow()
+          editor.addCursorAtBufferPosition([lastVisibleRow, 0])
+          spyOn(editor, 'scrollToPixelPosition')
+          buffer.insert([lastVisibleRow, 0], "\n\n")
+          expect(editor.scrollToPixelPosition).not.toHaveBeenCalled()
+          editor.insertText('\n\n')
+          expect(editor.scrollToPixelPosition.callCount).toBe 1
+
         describe "when the last cursor exceeds the upper or lower scroll margins", ->
           describe "when the editor is taller than twice the vertical scroll margin", ->
             it "sets the scrollTop so the cursor remains within the scroll margin", ->

src/app/selection.coffee

@@ -154,6 +154,7 @@ class Selection
     wasReversed = @isReversed()
     text = @normalizeIndent(text, options) if options.normalizeIndent
     @clear()
+    @cursor.needsAutoscroll = @cursor.isLastCursor()
     newBufferRange = @editSession.buffer.change(oldBufferRange, text)
     if options.select
       @setBufferRange(newBufferRange, reverse: wasReversed)