$ git clone -n https://src.fedoraproject.org/rpms/ghc-rpm-macros.git /var/lib/mock/f39-build-1918725-42936/root/chroot_tmpdir/scmroot/ghc-rpm-macros
Cloning into '/var/lib/mock/f39-build-1918725-42936/root/chroot_tmpdir/scmroot/ghc-rpm-macros'...
$ git fetch origin a8ecfed0e907e086ce71eac379553a3132cf0e3e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-rpm-macros
 * [new ref]         a8ecfed0e907e086ce71eac379553a3132cf0e3e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a8ecfed prepare 2.6.5