$ git clone -n https://src.fedoraproject.org/rpms/rust-uu_tac.git /var/lib/mock/f40-build-1971921-25224/root/chroot_tmpdir/scmroot/rust-uu_tac
Cloning into '/var/lib/mock/f40-build-1971921-25224/root/chroot_tmpdir/scmroot/rust-uu_tac'...
$ git fetch origin e820c6c56369659623da0849b82aaec43b261de9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-uu_tac
 * [new ref]         e820c6c56369659623da0849b82aaec43b261de9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e820c6c Update to version 0.0.27; Fixes: RHBZ#2260243