$ git clone -n https://src.fedoraproject.org/rpms/rubygem-crass.git /var/lib/mock/f40-build-2224110-52768/root/chroot_tmpdir/scmroot/rubygem-crass
Cloning into '/var/lib/mock/f40-build-2224110-52768/root/chroot_tmpdir/scmroot/rubygem-crass'...
$ git fetch origin 621b39bf3de7ec9819e191bdc0b1d474f6286609:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-crass
 * [new ref]         621b39bf3de7ec9819e191bdc0b1d474f6286609 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 621b39b Fix FTBFS due to Minitest 5.19+ incompatibility.