$ git clone -n https://src.fedoraproject.org/rpms/rubygem-gem2rpm.git /var/lib/mock/f45-build-34940-692/root/chroot_tmpdir/scmroot/rubygem-gem2rpm
Cloning into '/var/lib/mock/f45-build-34940-692/root/chroot_tmpdir/scmroot/rubygem-gem2rpm'...
$ git fetch origin 8c19cb5d6f8dd75971e09fda8f93aa37763062b0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-gem2rpm
 * [new ref]         8c19cb5d6f8dd75971e09fda8f93aa37763062b0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8c19cb5 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild