Include git commit sha hash and/or tag id in pipeline output(s)

[dfornika]

To facilitate reproducibility, auditability and re-analysis, this pipeline should automatically pull in information about exactly which version of this codebase was used to run a particular analysis.

The best identifier I can think of is the commit sha hash. Whichever identifiers are reported, it should enable another researcher to reproduce an analysis, potentially on a completely different system.