doc: Update README removing reference to obsolete post-receive web hook handler

This commit both removes reference to the `github-circleci-trigger` project
and improve the content.

Author: jcfr

README.md

@@ -2,43 +2,60 @@
 
 This project hosts the Slicer API documentation served from http://apidocs.slicer.org.
 
+## Automatic Generation and Publishing
 
-## Automatic generation
+The Slicer API documentation is automatically generated and published using a GitHub workflow. The
+generated files are pushed to the `gh-pages` branch, which is configured as the source for
+[GitHub Pages](https://help.github.com/articles/configuring-a-publishing-source-for-github-pages/).
 
-Documentation is automatically generated and pushed to the `gh-pages` branch configured as a [GitHub Pages](https://help.github.com/articles/configuring-a-publishing-source-for-github-pages/) source.
+### Workflow Triggers
 
-The [slicer-apidocs-builder](https://github.com/Slicer/slicer-apidocs-builder) tool is used within the GitHub workflow
-[doxygen-build-and-publish.yml](.github/workflows/.github/workflows/doxygen-build-and-publish.yml) to checkout Slicer source code, build doxygen documentation and publish generated html pages.
+The [trigger-doxygen-build-and-publish.yml](https://github.com/Slicer/Slicer/blob/main/.github/workflows/trigger-doxygen-build-and-publish.yml) workflow in the `Slicer/Slicer` repository initiates the process whenever:
+- The `main` branch is updated.
+- A new release tag is pushed.
 
-Each time the `main` branch of https://github.com/Slicer/Slicer is updated or each time a new release tag
-is pushed, the generated documentation is either added to the `main` folder or added to a new folder
-named after the release tag. Then the updated content is pushed to the `gh-pages` branch.
+### Documentation Generation
 
-The simple GitHub post-receive web hook handler triggering a CircleCI build is
-[github-circleci-trigger](https://github.com/Slicer/github-circleci-trigger). It is implemented as
-a Flask application hosted on a free heroku instance.
+The [slicer-apidocs-builder](https://github.com/Slicer/slicer-apidocs-builder) tool handles the
+generation and publication of documentation. It is invoked within the [doxygen-build-and-publish.yml](.github/workflows/doxygen-build-and-publish.yml) workflow maintained in this repository to:
 
-## Squash of `gh-pages` branch using a scheduled GitHub Actions worklfow
+1. Check out the Slicer source code.
+2. Build the Doxygen documentation.
+3. Publish the generated HTML files.
 
-After some time, the amount of data published on the `gh-pages` exceeds GitHub [recommended size of 1GB][max_size].
-To cleanup the repository, a [scheduled workflow][schedule] associated with this project
-will be triggered weekly and will execute [gh-pages-squash.sh](./gh-pages-squash.sh) script.
+### Documentation Updates
 
-The script simply do a soft reset, amend the first commit and force push the branch `gh-pages`.
+- **Main Branch Updates**: Documentation for the `main` branch is added to the `main` folder.
+- **Release Tags**: Documentation for new release tags is added to a folder named after the tag.
+
+The updated content is pushed to the `gh-pages` branch, ensuring the documentation remains current and accessible.
+
+## Managing the `gh-pages` Branch Size
+
+Over time, the size of the `gh-pages` branch may exceed GitHub's [recommended limit of 1GB][max_size].
+To manage this, a [scheduled workflow][schedule] is configured to run weekly. This workflow executes
+the [gh-pages-squash.sh](./gh-pages-squash.sh) script, which performs the following actions:
+1. Executes a soft reset.
+2. Amends the first commit.
+3. Force-pushes the `gh-pages` branch.
+
+This ensures that the repository size remains within the recommended limits.
 
 [max_size]: https://help.github.com/articles/what-is-my-disk-quota/
 [schedule]: https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#schedule
 
+## Programmatic Updates of the `gh-pages` Branch
 
-## Programmatically request updates of `gh-pages` branch using GitHub API
+You can manually trigger updates to the `gh-pages` branch using the GitHub API. This is
+useful for debugging or forcing a squash without waiting for the scheduled workflow.
 
 ### Prequisites
 
 * Generate GitHub token - See [here](https://github.com/settings/tokens)
 
 ### Squash *gh-pages*
 
-*This is useful to debug the workflow without having to wait.*
+To trigger the squash workflow programmatically, run the following command:
 
 ```
 GITHUB_TOKEN=<YOUR_GITHUB_TOKEN> ./trigger-workflow-squash.sh