Command line option for showing build version / git commit

[codeling]

Other exporters typically provide a --version command line option, which outputs the release version and the git commit the current build is based on. As far as I can tell (from looking at the "Usage" output), this functionality does not exist yet here. It would be very nice to have in this exporter as well though.

Thanks for all your hard work so far on this great exporter, and also in advance in case you implement this feature!