$ git clone -n https://src.fedoraproject.org/forks/imbearchild/rpms/ffmpeg.git /var/lib/mock/f38-build-side-42-init-devel-771842-27758/root/chroot_tmpdir/scmroot/ffmpeg
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-771842-27758/root/chroot_tmpdir/scmroot/ffmpeg'...
$ git fetch origin 305b72ff131ef9cffbdfc194c2c0805d1bd9f2e6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/imbearchild/rpms/ffmpeg
 * [new ref]         305b72ff131ef9cffbdfc194c2c0805d1bd9f2e6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 305b72f Add a patch to be compatible with qt5-webengine