variable git command in conf file

[ThomDietrich]

I wanted to make sure that the working copy on my deployment system is always an exact copy of the newest revision at github/origin. 'git fetch' is insufficient for that reason.
Change 1: git command is part of the config file
Change 2: config example
Remark: example command is hardcore and will delete all local changes.
git checkout: is redundant here but needed if you want to define a git post-checkout hook (i have one)

Cheers!