$ git clone -n https://src.fedoraproject.org/rpms/opencv.git /var/lib/mock/f40-build-1965556-25205/root/chroot_tmpdir/scmroot/opencv
Cloning into '/var/lib/mock/f40-build-1965556-25205/root/chroot_tmpdir/scmroot/opencv'...
$ git fetch origin b645eac1f17dd2c587e0ccc4a9cac1aef5d70c30:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/opencv
 * [new ref]         b645eac1f17dd2c587e0ccc4a9cac1aef5d70c30 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b645eac Reduce debuginfo level on i386 to avoid memory exhaustion