$ git clone -n https://src.fedoraproject.org/rpms/R-servr.git /var/lib/mock/f40-build-1930451-25111/root/chroot_tmpdir/scmroot/R-servr
Cloning into '/var/lib/mock/f40-build-1930451-25111/root/chroot_tmpdir/scmroot/R-servr'...
$ git fetch origin 4da9c0d9f4732961adc6bfff6406613788f3ad09:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-servr
 * [new ref]         4da9c0d9f4732961adc6bfff6406613788f3ad09 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4da9c0d R-maint-sig mass rebuild