Position decoration at top of line number when the first line is deleted

lib/git-diff-view.coffee

@@ -111,7 +111,10 @@ class GitDiffView
       if oldLines is 0 and newLines > 0
         @markRange(startRow, endRow, 'git-line-added')
       else if newLines is 0 and oldLines > 0
-        @markRange(startRow, startRow, 'git-line-removed')
+        if startRow < 0
+          @markRange(0, 0, 'git-previous-line-removed')
+        else
+          @markRange(startRow, startRow, 'git-line-removed')
       else
         @markRange(startRow, endRow, 'git-line-modified')
     return

spec/git-diff-spec.coffee

@@ -54,6 +54,15 @@ describe "GitDiff package", ->
       expect(editorView.querySelectorAll('.git-line-removed').length).toBe 1
       expect(editorView.querySelector('.git-line-removed')).toHaveData("buffer-row", 4)
 
+  describe "when the editor has removed the first line", ->
+    it "highlights the line preceeding the deleted lines", ->
+      expect(editorView.querySelectorAll('.git-line-added').length).toBe 0
+      editor.setCursorBufferPosition([0, 0])
+      editor.deleteLine()
+      advanceClock(editor.getBuffer().stoppedChangingDelay)
+      expect(editorView.querySelectorAll('.git-previous-line-removed').length).toBe 1
+      expect(editorView.querySelector('.git-previous-line-removed')).toHaveData("buffer-row", 0)
+
   describe "when a modified line is restored to the HEAD version contents", ->
     it "removes the diff highlight", ->
       expect(editorView.querySelectorAll('.git-line-modified').length).toBe 0

styles/git-diff.less

@@ -29,6 +29,22 @@ atom-text-editor {
       margin-top: -@size;
       pointer-events: none;
     }
+
+    &.git-previous-line-removed:before {
+      @size: 4px;
+
+      position: absolute;
+      left: 0;
+      top: 0;
+      height: 0;
+      width: 0;
+      content: " ";
+      border: solid transparent;
+      border-left-color: @syntax-color-removed;
+      border-width: @size;
+      margin-top: -@size;
+      pointer-events: none;
+    }
   }
   .gutter.git-diff-icon .line-number {
     width: 100%;