$ git clone -n https://src.fedoraproject.org/rpms/magic.git /var/lib/mock/f40-build-2201244-51815/root/chroot_tmpdir/scmroot/magic
Cloning into '/var/lib/mock/f40-build-2201244-51815/root/chroot_tmpdir/scmroot/magic'...
$ git fetch origin c06aad6925fd1ca424d6432292db9aff8d2ef0dd:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/magic
 * [new ref]         c06aad6925fd1ca424d6432292db9aff8d2ef0dd -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c06aad6 8.3.456