$ git clone -n https://src.fedoraproject.org/rpms/linbox.git /var/lib/mock/f39-build-1669593-40846/root/chroot_tmpdir/scmroot/linbox
Cloning into '/var/lib/mock/f39-build-1669593-40846/root/chroot_tmpdir/scmroot/linbox'...
$ git fetch origin 942f2fb1b006d96a6dee2c4a70bfb464731678b5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/linbox
 * [new ref]         942f2fb1b006d96a6dee2c4a70bfb464731678b5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 942f2fb Fix an undersized allocation