bling/vim-airline — pull request #396 by gstewart (2014-01-01 02:09:47+00:00)
Title: Fixed modified tab/buffer not updating in tabline

When a tab or buffer was modified, the hightlight group wasn't updated until you changed to a new tab or buffer. The current tabline was returned without rebuilding if the tab/buffer hand't been switched.

I tried this a couple different ways and went with this one since the same logic worked for both tabs and buffers. It stores the current &modified var by checking what the group was set to.