Generate repository README files from Org documents

By on 2023-04-26

A widespread standard amongst code hosting platforms is for repositories to have a file named README.md, which is then used as the description on the repository page. Generally, this file is written in Markdown, but other formats work too.

Aside from Markdown, GitHub support Org files too. However, the support for Org lacks most advanced features, producing HTML representations which include remnants of the Org files they’re generated from.1 Using a Markdown-based README still produces the most reliable results.

For example, all of the code for ox-md-title.el is written inside an Org document in an attempt to write its documentation and implementation in a single source file. With a setup like that, maintaining a separate README file defeats the purpose of having the Org file as a signgle source of truth. Instead, it’d be useful to generate the README—in Markdown format—from the Org file as well.

To generate a Markdown file from an Org document, run org-md-export-to-markdown in Emacs’ batch mode: 

emacs --batch ox-html-title.org --funcall org-md-export-to-markdown

This produces a Markdown representation of ox-html-title.org in ox-html-title.md.

readme.el

readme.el is a script to generate Markdown files from Org documents, aimed at producing repository README files to be used on GitHub. It has some advantages over running org-md-export-to-markdown:

  1. It uses ox-gfm to produce GitHub-flavored Markdown, a dialect of Markdown which adds some features, like fenced code blocks, which add syntax highlighting capabilities.
  2. It uses ox-md-title.el to add document titles to the produced Markdown documents, which is not enabled by default in Org mode’s Markdown exporters.
  3. It takes a filename, allowing a file named ox-html-title.org to produce a file named README.md instead of ox-html-title.md.

The package dependencies are vendored in, so they don’t need to be downloaded with a package manager. Instead, the script loads them from its local submodules, requires them, and sets up ox-md-title: 

(let ((directory (file-name-directory load-file-name)))
  (load (concat directory "ox-gfm/ox-gfm"))
  (load (concat directory "ox-md-title/ox-md-title")))

(require 'ox-gfm)
(require 'ox-md-title)
(org-md-title-add)

A function named readme/to-markdown is exposed, which is called to create the README file. Before generating the file, it turns on ox-md-title’s org-md-title option and disables backup file creation. Then it generates the Markdown file and stores it in the location passed via the filename argument: 

(defun readme/to-markdown (filename)
  (let ((org-md-title t)
	(make-backup-files nil))
    (org-gfm-export-as-markdown)
    (write-file filename)))

To run the script, run Emacs in --batch mode, open the file to be converted to Markdown (org-readme.org, for example), load readme.el and call the function with the desired output filename (README.md): 

emacs --batch org-readme.org --load readme.el --eval "(readme/to-markdown \"README.md\")"

To automatically generate README files on GitHub, add readme.el to your repository as a submodule and add a workflow that calls it. For example, the repository for readme.el includes a workflow that automatically updates its README:2 

name: README.md

on:
  push:
    branches: [ "main" ]

jobs:
  generate:
    runs-on: ubuntu-latest

    permissions:
      contents: write

    steps:
      - uses: actions/checkout@v3
	with:
	  submodules: true
      - uses: purcell/setup-emacs@master
	with:
	  version: 28.2
      - run: emacs --batch org-readme.org --load readme.el --eval "(readme/to-markdown \"README.md\")"
      - uses: stefanzweifel/git-auto-commit-action@v4
	with:
	  commit_message: Regenerate README.md

  1. For example, this document uses some features not supported by GitHub:

    1. Inline code blocks (src_org: +#title, src_html: <title>) aren’t replaced.
    2. Code blocks aren’t executed and :exports options are ignored, showing the code block when only the results should be included.
    3. Noweb doesn’t work, leaving unreplaced tags like <<template>> in the code blocks.
    4. Footnotes don’t work, meaning the reference ([fn:patch]) is left in the file and the footnote isn’t replaced with footnote markup.

    While the inline code blocks and footnotes could be fixed, it’s no surprise that the code blocks aren’t executed and files aren’t tangled.

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  2. Other projects that use readme.el in their workflows include ox-md-title.el and ox-html-stable-ids.el.

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