When lines are added, remove any that get pushed down to exceed the max allowed row

This fixes issues where unfolding or pasting caused rendering artifacts below the last visible row.

spec/app/editor-spec.coffee

@@ -470,6 +470,24 @@ describe "Editor", ->
           expect(editor.gutter.find('.line-number:last').text()).toBe '13'
           expect(editor.gutter.find('.line-number').length).toBe 13
 
+      describe "when lines are folded, then the editor becomes shorter before the lines are unfolded", ->
+        it "renders the lines and line numbers correctly after unfolding", ->
+          fold = editor.createFold(1, 9)
+          setEditorHeightInLines(editor, 4.5)
+
+          fold.destroy()
+
+          expect(editor.visibleLines.find('.line').length).toBe 7
+          expect(editor.visibleLines.find('.line:last').text()).toBe buffer.lineForRow(6)
+
+          expect(editor.gutter.find('.line-number').length).toBe 7
+          expect(editor.gutter.find('.line-number:last').text()).toBe '7'
+
+          editor.scrollTop(3 * editor.lineHeight)
+
+          expect(editor.visibleLines.find('.line').length).toBe 9
+          expect(editor.visibleLines.find('.line:last').text()).toBe buffer.lineForRow(9)
+
     describe "when some lines at the end of the buffer are not visible on screen", ->
       beforeEach ->
         editor.attachToDom(heightInLines: 5.5)
@@ -602,9 +620,9 @@ describe "Editor", ->
           expect(editor.visibleLines.find(".line:last").text()).toBe buffer.lineForRow(12)
 
           buffer.change([[2,0], [7,0]], "2\n3\n4\n5\n6\n7\n8\n9\n")
-          expect(editor.visibleLines.find(".line").length).toBe 10
+          expect(editor.visibleLines.find(".line").length).toBe 9
           expect(editor.visibleLines.find(".line:first").text()).toBe buffer.lineForRow(6)
-          expect(editor.visibleLines.find(".line:last").text()).toBe buffer.lineForRow(15)
+          expect(editor.visibleLines.find(".line:last").text()).toBe buffer.lineForRow(14)
 
       describe "when the change straddles the last rendered row", ->
         it "doesn't render rows that were not previously rendered", ->

src/app/editor.coffee

@@ -452,7 +452,7 @@ class Editor extends View
       firstVisibleScreenRow = @getFirstVisibleScreenRow()
       lastVisibleScreenRow = @getLastVisibleScreenRow()
 
-      maxEndRow = Math.max(lastVisibleScreenRow, @lastRenderedScreenRow)
+      maxEndRow = Math.max(lastVisibleScreenRow + @lineOverdraw, @lastRenderedScreenRow)
       @gutter.renderLineNumbers(@firstRenderedScreenRow, maxEndRow) if e.lineNumbersChanged
       @verticalScrollbarContent.height(@lineHeight * @screenLineCount())
 
@@ -480,6 +480,9 @@ class Editor extends View
       rowDelta = newScreenRange.end.row - oldScreenRange.end.row
       @lastRenderedScreenRow += rowDelta
       @updateVisibleLines() if rowDelta < 0
+      if @lastRenderedScreenRow > maxEndRow
+        @removeLineElements(maxEndRow + 1, @lastRenderedScreenRow)
+        @lastRenderedScreenRow = maxEndRow
 
   buildLineElements: (startRow, endRow) ->
     charWidth = @charWidth