The drawback to the native `%include` Kickstart directive is that it
requires a static, hard-coded, absolute path. This means that we
cannot, for example, host a copy of the kickstarts from a different
branch for testing, without modifying the URLs of all the included
files.
Switching to using Jinja templates introduces a build step, but the
result is that the artifacts are self-contained. This way, they can be
deployed anywhere. I'm not sure where I'll put them, though, and
they'll need a Jenkins job to run the build and publish them.
