Nested folds can start at the same row as the fold that contains them

...still need to test destroying the outer fold though.

spec/app/renderer-spec.coffee

@@ -316,10 +316,16 @@ describe "Renderer", ->
           expect(line6.screenDelta).toEqual [1, 0]
           expect(line7.text).toBe '8'
 
-        it "allows the outer fold to start at the same location as the inner fold", ->
-          renderer.createFold([[4, 29], [7, 4]])
-          renderer.createFold([[4, 29], [9, 2]])
-          expect(renderer.lineForRow(4).text).toBe "    while(items.length > 0) {...};"
+        fit "allows the outer fold to start at the same location as the inner fold", ->
+          innerFold = renderer.createFold(4, 6)
+          outerFold = renderer.createFold(4, 8)
+
+          [line4, line5] = renderer.linesForRows(4, 5)
+          expect(line4.fold).toBe outerFold
+          expect(line4.text).toMatch /4-+/
+          expect(line4.bufferDelta).toEqual [5, 0]
+          expect(line4.screenDelta).toEqual [1, 0]
+          expect(line5.text).toMatch /9-+/
 
       describe "when a fold begins on the line on which another fold ends", ->
         describe "when the second fold is created before the first fold", ->

src/app/renderer.coffee

@@ -137,7 +137,7 @@ class Renderer
     while startBufferRow <= endBufferRow
       screenLine = @highlighter.lineForRow(startBufferRow)
 
-      if fold = @foldForBufferRow(startBufferRow)
+      if fold = @largestFoldForBufferRow(startBufferRow)
         screenLine = screenLine.copy()
         screenLine.fold = fold
         screenLine.bufferDelta = fold.getBufferDelta()
@@ -184,8 +184,9 @@ class Renderer
     _.remove(folds, fold)
     delete @foldsById[fold.id]
 
-  foldForBufferRow: (bufferRow) ->
-    @activeFolds[bufferRow]?[0]
+  largestFoldForBufferRow: (bufferRow) ->
+    return unless folds = @activeFolds[bufferRow]
+    (folds.sort (a, b) -> b.endRow - a.endRow)[0]
 
   buildFoldPlaceholder: (fold) ->