$ git clone -n https://src.fedoraproject.org/rpms/rust-dav1d.git /var/lib/mock/f42-build-side-1-3540447-46574/root/chroot_tmpdir/scmroot/rust-dav1d
Cloning into '/var/lib/mock/f42-build-side-1-3540447-46574/root/chroot_tmpdir/scmroot/rust-dav1d'...
$ git fetch origin 4b7636f148084812de0036e7a7d491aae8177fb8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-dav1d
 * [new ref]         4b7636f148084812de0036e7a7d491aae8177fb8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4b7636f Update to version 0.10.4; Fixes RHBZ#2357595