$ git clone -n https://src.fedoraproject.org/rpms/rubygem-git.git /var/lib/mock/f41-build-side-1-2849159-33909/root/chroot_tmpdir/scmroot/rubygem-git
Cloning into '/var/lib/mock/f41-build-side-1-2849159-33909/root/chroot_tmpdir/scmroot/rubygem-git'...
$ git fetch origin ad2d13507d097e15f66028a25772b677863243b1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-git
 * [new ref]         ad2d13507d097e15f66028a25772b677863243b1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ad2d135 Re-enable most of test suite.