$ git clone -n https://src.fedoraproject.org/rpms/rust-git2.git /var/lib/mock/f40-build-2566229-62190/root/chroot_tmpdir/scmroot/rust-git2
Cloning into '/var/lib/mock/f40-build-2566229-62190/root/chroot_tmpdir/scmroot/rust-git2'...
$ git fetch origin 5afbce9cccd727f15f8edd347a77c7279b73af44:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-git2
 * [new ref]         5afbce9cccd727f15f8edd347a77c7279b73af44 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5afbce9 Update to version 0.18.2; Fixes RHBZ#2263124