$ git clone -n https://src.fedoraproject.org/rpms/golang-github-letsencrypt-challtestsrv.git /var/lib/mock/f45-build-12187-439/root/chroot_tmpdir/scmroot/golang-github-letsencrypt-challtestsrv
Cloning into '/var/lib/mock/f45-build-12187-439/root/chroot_tmpdir/scmroot/golang-github-letsencrypt-challtestsrv'...
$ git fetch origin 24d391a2fe62f9cac193d2b3b07bfc4950e82f96:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/golang-github-letsencrypt-challtestsrv
 * [new ref]         24d391a2fe62f9cac193d2b3b07bfc4950e82f96 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 24d391a Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild