Git describe

Show git describe in log dialog.
How about this :-)
![spaces](https://cloud.githubusercontent.com/assets/5831804/4675076/42cb879e-5608-11e4-83ec-e876ed9a5812.png)
If you want it, it is [here](https://github.com/YueLinHo/TortoiseGit/commit/b706f17e777d655fed15241fae25a1a6aa969021).