$ git clone -n https://src.fedoraproject.org/rpms/rust-jobserver.git /var/lib/mock/f39-build-1466986-33712/root/chroot_tmpdir/scmroot/rust-jobserver
Cloning into '/var/lib/mock/f39-build-1466986-33712/root/chroot_tmpdir/scmroot/rust-jobserver'...
$ git fetch origin 6bb421aab2acc1569f8459312c98b48b20755ea0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-jobserver
 * [new ref]         6bb421aab2acc1569f8459312c98b48b20755ea0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6bb421a Update to version 0.1.27; Fixes RHBZ#2243056