Adding backlinks to a GitHub wiki

Backlinks, or bi-directional liks, are becoming table-stakes for productivity apps since they've been popularized by Roam. It's a simple concept: when you create a link from page A to page B, page B will also reference page A. With traditional hyperlinks, page B wouldn't know about page A unless you explicitly link it back.

Backlinks allow a graph of knowledge to grow organically. When you create a doc for Orders, and mention Products, a Products page will be created or updated with a backlink. Even when not actively documenting Products, readers can get an idea of what they entail because of the linked references.

For example, Orders might reference Products.

Orders contain one or more [[Products]].

A system that supports backlinks would add a reference to the Products page.

## Backlinks
- [[Orders]]
- Orders contain one or more [[Products]].

Sometimes we use GitHub wiki for documentation. Documenting a large system can be difficult because there are a lot of interdependencies, and it's not always obvious where something belongs. This is a challange for the writer (where does this go?) and for the reader (where can I find this?). Backlinks help out because they ensure something is mentioned in multiple places where relevant.

GitHub wikis are based on Markdown files. They're also a plain git repository that supports GitHub Actions, so you can automate tasks. Andy Matuschak created note-link-janitor, a script that crawls files and adds backlinks to your Markdown notes. A fork of the script is also available as a GitHub Action, which you can configure to run whenever your wiki is updated.

Note-link-janitor indexes all your wiki style links, and creates a References section on the bottom of each page with backlinks.

To enable note-link-janitor, create a workflow file.

# .github/workflows/note-link-janitor.yml
name: Note Link Janitor
runs-on: self-hosted
- uses: actions/checkout@v2
repository: ${{github.repository}}.wiki
- uses: sander/note-link-janitor@v5

This workflow will run whenever the wiki is updated (the gollum event), or when triggered manually (workflow_dispatch). Whenever you use wiki-style links in your documentation, the Action will push a commit with newly generated backlinks.