$ git clone -n https://src.fedoraproject.org/rpms/rubygem-ffi.git /var/lib/mock/f42-build-865175-172845/root/chroot_tmpdir/scmroot/rubygem-ffi
Cloning into '/var/lib/mock/f42-build-865175-172845/root/chroot_tmpdir/scmroot/rubygem-ffi'...
$ git fetch origin 2bb4dd8b95bf6aedda1b0ceedabe8c903c437f40:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-ffi
 * [new ref]         2bb4dd8b95bf6aedda1b0ceedabe8c903c437f40 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2bb4dd8 Rebuilt for https://fedoraproject.org/wiki/Changes/Ruby_3.4