$ git clone -n https://src.fedoraproject.org/rpms/rust-git2.git /var/lib/mock/f38-build-side-42-init-devel-1393729-31050/root/chroot_tmpdir/scmroot/rust-git2
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1393729-31050/root/chroot_tmpdir/scmroot/rust-git2'...
$ git fetch origin 8157091e832ae03121e3f01c0fa21cf95c5336cf:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-git2
 * [new ref]         8157091e832ae03121e3f01c0fa21cf95c5336cf -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8157091 Update to version 0.18.0; Fixes RHBZ#2235482