To get the short version of a Git revision.
git rev-parse --short HEAD
The short version is the first 6 character of the sha1 that is the full version.
The following script first gets the current revision for HEAD, then calls the same command for the short revision:
$ git rev-parse HEAD
edc24971b373d63023e30175aacd8fd264cc0584
$ git rev-parse --short HEAD
edc2497
$