Add git version parsing test for git 2.0.0 as seen in Debian testing
Test to confirm JENKINS-23424 is a bug in our JGit implementation

JENKINS-23424 reports that a tracked file which is locally modified is
not reset to its original content on the next checkout when using our
JGit implementation.  It is reset to its original content when using
our command line git implementation.
Merge commit '48fe77daa9c05ddcff4c57f2c163c800028ad955' into HEAD