The function returns the latest git commit and branch for the repo specified
in repo
or the current working directory if unspecified.
Git is needed for the command to run.
The functions makes it possible to include the latest git commit and branch
in a run to be able to know exactly which code where used.
git_stamp(repo = getwd())
character vector with latest commit and branch
Git repo directory. If unspecified, then the current working directory is used.