$ git clone -n https://src.fedoraproject.org/rpms/rubygem-actionpack.git /var/lib/mock/f42-build-3458005-45512/root/chroot_tmpdir/scmroot/rubygem-actionpack
Cloning into '/var/lib/mock/f42-build-3458005-45512/root/chroot_tmpdir/scmroot/rubygem-actionpack'...
$ git fetch origin 46d87d445a6d09f5fe78d3ba80ee9418f2e955be:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-actionpack
 * [new ref]         46d87d445a6d09f5fe78d3ba80ee9418f2e955be -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 46d87d4 Fix Rack::Test 2+ test compatibility.