$ git clone -n https://src.fedoraproject.org/rpms/rubygem-concurrent-ruby.git /var/lib/mock/f45-build-34875-692/root/chroot_tmpdir/scmroot/rubygem-concurrent-ruby
Cloning into '/var/lib/mock/f45-build-34875-692/root/chroot_tmpdir/scmroot/rubygem-concurrent-ruby'...
$ git fetch origin 4e4c334e2aa4fde9d843d4caf8812704a6c1b8b5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-concurrent-ruby
 * [new ref]         4e4c334e2aa4fde9d843d4caf8812704a6c1b8b5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4e4c334 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild