A Changelog is a file that documents changes made to a codebase.
In its simplest form, it's a plain text file within a code repository, or it can be written in Markdown or reStructuredText or kept within a separate tool like Confluence or Sharepoint. Regardless of where it's kept, the main thing is the content.
It's not a copy of the Git log. It's a summary of the changes to be read by humans and for them to see what's changed, not a list of Git commits.
If you're considering using my open-source package, you can see what changes I've released, when, and what changes are due to release.
## How is it structured?
Each version should have a heading specifying the version number and/or release date and a list of changes grouped by their type - whether something was added, changed, deprecated, removed, etc. This works well if you use conventional commits!
I like to follow a format called [Keep a Changelog](https://keepachangelog.com).
The headings link to a diff so you can see all of the commits and changes made to the code, and there's an `Unreleased` section that shows commits that have yet to be tagged and released.
If you need to present changes to a review or approval board, having an easy-to-read list of changes, separated by their type, is a much clearer format than a list of Git commits.
## When should it be updated?
I recommend continually updating the Changelog rather than leaving it to just before a deployment. It's quick to add it to the `Unreleased` section as part of the commit and update the headings later.
## Can I see an example?
Sure. See the one I added to the [National Rail Enquiries feed parser library](https://github.com/opdavies/national-rail-enquiries-feed-parser/blob/main/CHANGELOG.md) I've been working on or the [Tailwind CSS starter kit theme for Drupal](https://git.drupalcode.org/project/tailwindcss/-/blob/5.x/CHANGELOG.md).
