$ git clone -n https://src.fedoraproject.org/rpms/csdiff.git /var/lib/mock/f40-build-780378-130937/root/chroot_tmpdir/scmroot/csdiff
Cloning into '/var/lib/mock/f40-build-780378-130937/root/chroot_tmpdir/scmroot/csdiff'...
$ git fetch origin a5a2ccc118f38471881bc930a331c95cf7b68fb2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/csdiff
 * [new ref]         a5a2ccc118f38471881bc930a331c95cf7b68fb2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a5a2ccc fix the last change log entry