Add PR preview in CI for easier review

[ncclementi]

So this PR includes a generated preview of the site that is built based on the PR. That way it'll be easier to review in the future. It only works from branches PRs, if the PR comes from a fork, it skips the workflow because it's not possible to run it due to security (the GHA does not work, so to avoid the error we skip it directly.

A maintainer will have to run from local. I added this into the CONTRIBUTING.md.

• For some reason (I think it might be a DNS thing, but I'm not sure). Even though the action creates a https preview link, when opening, it shows as http and it says not secure, it's unclear why to me.

• Note: There were some hard-coded paths, that were breaking being able to render well the preview. Claude suggested using relative paths, and that worked.

Some of the changes needed to make this work:

┌────────────────────────┬─────────────────────────────────────────────────────────────────────────────────┐                                              
  │          File          │                                       Fix                                       │                                              
  ├────────────────────────┼─────────────────────────────────────────────────────────────────────────────────┤                                              
  │ _layouts/homepage.html │ Logo src, event.image src, event-interest-form link, /blog/ link, /donate/ link │                                              
  ├────────────────────────┼─────────────────────────────────────────────────────────────────────────────────┤
  │ _layouts/donate.html   │ Logo src                                                                        │                                              
  ├────────────────────────┼─────────────────────────────────────────────────────────────────────────────────┤                                              
  │ _includes/header.html  │ Logo src                                                                        │
  ├────────────────────────┼─────────────────────────────────────────────────────────────────────────────────┤                                              
  │ _includes/footer.html  │ Root href="/", /donate/ link                                                    │                                              
  ├────────────────────────┼─────────────────────────────────────────────────────────────────────────────────┤                                              
  │ community.markdown     │ Event-interest-form link                                                        │
  └────────────────────────┴─────────────────────────────────────────────────────────────────────────────────┘

Every hardcoded /path is now wrapped with {{ '...' | relative_url }}, so they'll respect baseurl in both production and previews. The data file paths in
_data/event_highlights.yml are handled at the template level (the {{ event.image | relative_url }} fix in homepage.html), so they don't need to change.

{{ '...' | relative_url }}

In Jekyll's Liquid templating language:

• {{ }} — outputs a value into the HTML
• '...' — a string literal (the path you're providing)
• | — a pipe that passes the value on the left into a filter on the right
• relative_url — a Jekyll filter that prepends site.baseurl to the path

So {{ '/blog/' | relative_url }} works like this:

• When baseurl: "" (production): outputs /blog/
• When baseurl: "/pr-preview/pr-17" (preview): outputs /pr-preview/pr-17/blog/

For the data file case, {{ event.image | relative_url }} does the same thing but reads the path from a variable instead of a string literal.

[github-actions]

PR Preview Action v1.8.1
Preview removed because the pull request was closed.
2026-02-25 15:05 UTC

[camclay]

LGTM Approved!