A one-line version of the SVN-REVISION hack on https://github.com/wch/r-source/wiki:
printf "Revision: %s\nLast Changed Date: %s\n" `git log --format=%B -n 1 | tr '\n' ' ' | sed -E 's/.*git-svn-id: https:\/\/svn.r-project.org\/R\/[^@]*@([0-9]+).*/\1/'` `git log -1 --pretty=format:"%ad" --date=iso | sed -E 's/ .*//'` > SVN-REVISION