$ git clone -n https://src.fedoraproject.org/rpms/rust-libtest-mimic.git /var/lib/mock/f38-build-side-43-rust-devel-1416661-31457/root/chroot_tmpdir/scmroot/rust-libtest-mimic
Cloning into '/var/lib/mock/f38-build-side-43-rust-devel-1416661-31457/root/chroot_tmpdir/scmroot/rust-libtest-mimic'...
$ git fetch origin b1d688a6010621bea3765e77f31f1b6395cb5227:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-libtest-mimic
 * [new ref]         b1d688a6010621bea3765e77f31f1b6395cb5227 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b1d688a Initial package (rhbz#2239036)