$ git clone -n https://src.fedoraproject.org/rpms/ffmpegthumbs.git /var/lib/mock/f39-build-1572237-37783/root/chroot_tmpdir/scmroot/ffmpegthumbs
Cloning into '/var/lib/mock/f39-build-1572237-37783/root/chroot_tmpdir/scmroot/ffmpegthumbs'...
$ git fetch origin 35208939428b9670dbf81c3c5d3b8b8b93b86043:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ffmpegthumbs
 * [new ref]         35208939428b9670dbf81c3c5d3b8b8b93b86043 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3520893 23.08.2