Jekyll Git commit

Published 2025-02-28 on Farid Zakaria's Blog

I wanted to include a hyperlink on my blog that included the commit it was published with.

Being a newbie in Jekyll, I did what anyone would do and asked the Internet which pointed me towards: jekyll-github-metadata.

This plugin worked well enough, except it needs network access on builds which didn’t work when I wanted to build my software with Nix.

There was no way to disable the network calls if I knew all the Git information I needed ahead of time.

Let’s do something simpler! We can write an incredibly simple Jekyll plugin that will provide a variable with the commit_hash for use in our pages. Place the following file in _plugins/git_commit.rb.

module Jekyll
  class GitCommitGenerator < Generator
    priority :highest

    def generate(site)
      commit_hash = ENV['JEKYLL_BUILD_REVISION'] ||
            `git rev-parse HEAD`.strip
      site.config['commit_hash'] = commit_hash
    end
  end
end

I have also included an environment variable JEKYLL_BUILD_REVISION, which if present, has the plugin short-circuit.

Our view commit source hyperlink is now pretty simple to cook up.

<p>
  <a href="https://github.com/org/repo/tree/{{ site.commit_hash }}/{{ page.path }}"
  >Improve this page @ {{ site.commit_hash | slice: 0, 7 -}}
  </a>
</p>

🥳 Simplified our build by removing dependencies and removed the necessity of having network access to build our blog.

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Improve this page @ 6e2f25c
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