$ git clone -n https://src.fedoraproject.org/rpms/kiss-fft.git /var/lib/mock/f39-build-2401850-60554/root/chroot_tmpdir/scmroot/kiss-fft
Cloning into '/var/lib/mock/f39-build-2401850-60554/root/chroot_tmpdir/scmroot/kiss-fft'...
$ git fetch origin b3a1867a450678eb0d6cef97dcec129fd3ca3616:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/kiss-fft
 * [new ref]         b3a1867a450678eb0d6cef97dcec129fd3ca3616 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b3a1867 New source