rebuild thumbnail sizes file in build action

[iainmcampbell]

Description

• defect | github pages workflow automated creation of category and tag pages does not pass to hosted artefact #2

Extracted the thumbnail sizes functionality into its own shell script and added it to the build action.

How to Test

Since the build action runs on pushes to main, to test this we can either temporarily change this and deploy from this branch, or merge this PR to main and then test it.

Now, when we add a JPG image to assets/images/hacknights/thumbnails, the build script should include its data in the generated thumbs.json file. The JPG image should be a different aspect ratio than square and different dimensions than 300x300, because those are the defaults:

civictech.ca/assets/js/lazy-image.js

Lines 37 to 39 in 09e1484

	const dimensions = dimensionsList[imageName]
	? dimensionsList[imageName].split(',')
	: [300, 300];

Notes

We aren’t committing any of the generated artifacts from the build script back into the repo, which is fine. doing so could create an infinite loops. the only downside is if you run the site locally, you won't have the most up to date build unless you manually run the build command, which will create a bunch of changes in the repo.

It would be ideal to not commit any of the generated artifacts to the repo, as they can be derived using the build script. You’d just need to run the build script locally before running the server for the first time.

To do

• get the derived files out of git
• bundle the build script using the makefile
• update readme

[Copilot]

Pull Request Overview

This PR adds a dedicated script to generate a JSON file of thumbnail dimensions, removes JSON logic from the existing image script, and integrates the new script into the CI workflow.

• Introduce _scripts/thumbnail_sizes.sh to scan thumbnails and emit thumbs.json.
• Strip JSON handling out of _scripts/img.sh.
• Update .github/workflows/pages.yml to run the new script and auto-commit its output.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
_scripts/thumbnail_sizes.sh	New script to collect thumbnail dimensions into a JSON file
_scripts/img.sh	Removed inline thumbnail JSON generation
.github/workflows/pages.yml	Added workflow steps to run thumbnail script and commit changes

Comments suppressed due to low confidence (3)

_scripts/thumbnail_sizes.sh:14

• The \n in the format string adds a newline into the variable, which will break JSON formatting. Use -format "%w,%h" (no newline) and append newlines only via echo or printf.

  dimensions=$(magick identify -format "%w,%h\n" "$thumb")

.github/workflows/pages.yml:53

• Pushing commits on a push event will trigger the workflow again, causing a loop. Add a condition to skip runs when the actor is GitHub Actions or include [ci skip] in the commit message.

      - name: 🚀 Commit and push changes

.github/workflows/pages.yml:1

• [nitpick] The job name Build artifacts no longer reflects building or deploying pages. Consider renaming to something like Generate and Commit Thumbnails for clarity.

name: Build artifacts

[iainmcampbell]

@alexwolson this PR is a draft, I'll mark it as ready for review once it's ready for review

[jordyarms]

For reference: I implemented a couple gems on CivicTechTO/civic-spark.com#8 that may be applicable to our problem space.