$ git clone -n https://src.fedoraproject.org/rpms/perl-Mixin-ExtraFields.git /var/lib/mock/f45-build-24796-606/root/chroot_tmpdir/scmroot/perl-Mixin-ExtraFields
Cloning into '/var/lib/mock/f45-build-24796-606/root/chroot_tmpdir/scmroot/perl-Mixin-ExtraFields'...
$ git fetch origin 3681d0e87f6ea96b10787c6f9a1c49bbec0768e8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Mixin-ExtraFields
 * [new ref]         3681d0e87f6ea96b10787c6f9a1c49bbec0768e8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3681d0e Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild