在R代码中显示Git版本

I am using Git as a version control (currently the centralised workflow, but I would like to move to feature branch or gitflow workflow). I use RStudio/Knitr to compile PDF documents and would like to know how I can automatically include the current Git version in the PDF - if that works? That way, when somebody comes back to me with a document I have given them, I know how to return to that point in the code. Any suggestions will be much appreciated, thanks - Marie.I am using Git as a version control (currently