$ git clone -n https://src.fedoraproject.org/rpms/R-stringr.git /var/lib/mock/f40-build-1930446-25111/root/chroot_tmpdir/scmroot/R-stringr
Cloning into '/var/lib/mock/f40-build-1930446-25111/root/chroot_tmpdir/scmroot/R-stringr'...
$ git fetch origin 67f356927d022283f46737a5f726fa8f7e447484:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-stringr
 * [new ref]         67f356927d022283f46737a5f726fa8f7e447484 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 67f3569 R-maint-sig mass rebuild