$ git clone -n https://src.fedoraproject.org/rpms/rust-ringbuf.git /var/lib/mock/f45-build-44432-813/root/chroot_tmpdir/scmroot/rust-ringbuf
Cloning into '/var/lib/mock/f45-build-44432-813/root/chroot_tmpdir/scmroot/rust-ringbuf'...
$ git fetch origin 86806a6b27725185413c22e9a797d17e2a6481e9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-ringbuf
 * [new ref]         86806a6b27725185413c22e9a797d17e2a6481e9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 86806a6 Update to 0.5.1 (fedora#2499895).