$ git clone -n https://src.fedoraproject.org/rpms/postfix.git /var/lib/mock/f42-build-862653-170994/root/chroot_tmpdir/scmroot/postfix
Cloning into '/var/lib/mock/f42-build-862653-170994/root/chroot_tmpdir/scmroot/postfix'...
$ git fetch origin 979433fd55a9ab13420321454b157f8fcd01d6a8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/postfix
 * [new ref]         979433fd55a9ab13420321454b157f8fcd01d6a8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 979433f Fixed postlog RPM verification