$ git clone -n https://src.fedoraproject.org/rpms/rubygem-execjs.git /var/lib/mock/f45-build-34913-692/root/chroot_tmpdir/scmroot/rubygem-execjs
Cloning into '/var/lib/mock/f45-build-34913-692/root/chroot_tmpdir/scmroot/rubygem-execjs'...
$ git fetch origin 072b408a3dd14a7b9040fbc088d65b99167475f2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-execjs
 * [new ref]         072b408a3dd14a7b9040fbc088d65b99167475f2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 072b408 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild