$ git clone -n https://src.fedoraproject.org/rpms/python-mailer.git /var/lib/mock/f45-build-31451-652/root/chroot_tmpdir/scmroot/python-mailer
Cloning into '/var/lib/mock/f45-build-31451-652/root/chroot_tmpdir/scmroot/python-mailer'...
$ git fetch origin 51de51ae9cf916314816ee586beddc3f844148f1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/python-mailer
 * [new ref]         51de51ae9cf916314816ee586beddc3f844148f1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 51de51a Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild