The GIT_REVISION is set as the result of 'git describe'.
If git is not installed the old code generated an error:
$ dh_autoreconf -a
sh: 1: git: not found
sh: 1: git: not found
Thanks to Thomas Hood for the bug report
https://groups.google.com/d/msg/nfc-tools-devel/Skd03b1wUcg/xnQThAPXPCYJ