$ git clone -n https://src.fedoraproject.org/forks/hypersa/rpms/ghc-dec /var/lib/mock/f39-build-2227245-53002/root/chroot_tmpdir/scmroot/ghc-dec
Cloning into '/var/lib/mock/f39-build-2227245-53002/root/chroot_tmpdir/scmroot/ghc-dec'...
$ git fetch origin 407d27f00fd271d39a2c294aa57f60a3e59def26:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/hypersa/rpms/ghc-dec
 * [new ref]         407d27f00fd271d39a2c294aa57f60a3e59def26 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 407d27f rebuild