$ git clone -n https://src.fedoraproject.org/rpms/ghc-boomerang.git /var/lib/mock/f45-build-10046-412/root/chroot_tmpdir/scmroot/ghc-boomerang
Cloning into '/var/lib/mock/f45-build-10046-412/root/chroot_tmpdir/scmroot/ghc-boomerang'...
$ git fetch origin e1e753e7bbd8120806892e30ec5afe103ef341ff:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-boomerang
 * [new ref]         e1e753e7bbd8120806892e30ec5afe103ef341ff -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e1e753e Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild