set current_revision by `git rev-parse HEAD`

Missing sha on `revision.log`. so I set current_revision by git command.

current:
```log
Branch master (at ) deployed as release 20140123030204 by linyows;
```

new:
```log
Branch master (at 3b23a5325c6195b35c219f58c01234b0c2abc579) deployed as release 20140123030523 by linyows;
```