$ git clone -n https://src.fedoraproject.org/rpms/rubygem-serialport.git /var/lib/mock/f40-build-2215309-52422/root/chroot_tmpdir/scmroot/rubygem-serialport
Cloning into '/var/lib/mock/f40-build-2215309-52422/root/chroot_tmpdir/scmroot/rubygem-serialport'...
$ git fetch origin 12bac47e7ad541bcdb0d5ac86e7c5ddd9739287f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-serialport
 * [new ref]         12bac47e7ad541bcdb0d5ac86e7c5ddd9739287f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 12bac47 Fix C compatibility issue