$ git clone -n https://src.fedoraproject.org/rpms/git.git /var/lib/mock/f42-build-side-1-3587359-46931/root/chroot_tmpdir/scmroot/git
Cloning into '/var/lib/mock/f42-build-side-1-3587359-46931/root/chroot_tmpdir/scmroot/git'...
$ git fetch origin f8bcf50ac88ad7dc9e6b853026fc45376b3a8975:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/git
 * [new ref]         f8bcf50ac88ad7dc9e6b853026fc45376b3a8975 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f8bcf50 update to 2.50.1