Automate GitHub Releases with CircleCI

This article was originally posted on CircleCI's blog.

Releases is a GitHub feature that allows you to present significant snapshots of your code, marked with a git tag, in GitHub's nice UI. If you're not currently using releases, I want to show you why you might want to, and how to implement them automatically.

With releases, you get what tags provide--a version number and description--but you also get a longer section for release notes and a place to store and display release artifacts. This means your software's binary, .deb, .rpm, and AppImage files will be hosted by GitHub for each release, providing a convenient place for users to install your software.

In this post, I will show you how to create releases within CircleCI. For a more general overview, see GitHub's doc on creating releases.

At its core, GitHub Releases is simply a GitHub feature layered on top of git tags. Let's break it down:

Git tags

Git tags give you a version number to mark a specific git commit as well as a short description. Believe it or not, just pushing a git tag to GitHub will create a new release in the "Releases" tab of your project on GitHub. This is a barebones release that includes only the tag information.

Releases

Releases add to git tags by providing a longer, "rich" description, the ability to mark the tag as a normal release or a pre-release, and most importantly, the ability to upload artifacts such as binaries for that release. Uploading these artifacts from CircleCI is what we're going to walk through here.

Tools

There are a few ways to publish artifacts from a CircleCI build to a GitHub Release:

• manually with curl and the GitHub API
• using GitHub Release
• using GotHub (a GitHub Release fork)
• and using ghr, which is what we'll use in our example

Using ghr

The ghr command full details can be found on GitHub, however, we really only need to learn one subcommand:

ghr -t ${GITHUB_TOKEN} -u ${CIRCLE_PROJECT_USERNAME} -r ${CIRCLE_PROJECT_REPONAME} -c ${CIRCLE_SHA1} -delete ${VERSION} ./artifacts/

This command uploads specific artifacts, typically binaries, to our GitHub release on GitHub. Let's break this down:

• ghr -t ${GITHUB_TOKEN} - Here we start the command and pass it a GitHub token for authentication. This is a GitHub Personal Access Token and not an OAuth token/key.

Specifically created via your personal GitHub account, you'll want to safeguard this token and only load it into the CircleCI environment via a private environment variable.

• -u ${CIRCLE_PROJECT_USERNAME} -r ${CIRCLE_PROJECT_REPONAME} - This is where we pass the GitHub user/org name and the repository name. Both values are passed via built-in CircleCI Environment Variables. No extra work is needed.

• -c ${CIRCLE_SHA1} - Here we provide the Git commit hash (available in CircleCI as $CIRCLE_SHA1) to ghr. This tells it which commit, and thus tag, the release is for.

• -delete - This deletes the git tag and release if it already exists.

• ${VERSION} - We set the git tag/release version via a $VERSION environment variable. This can be any variable you want or a string. Typically this is the same as the version of your software release.

• ./artifacts/ - Then we set the PATH to find the artifacts. In this case, everything in a directory called artifacts inside the current directory.

Plain CircleCI 2.0 example

We've walked through how to use ghr to create a GitHub Release but let's see how it can look inside of a CircleCI 2.0 configuration file:

  publish-github-release:
    docker:
      - image: circleci/golang:1.8
    steps:
      - attach_workspace:
          at: ./artifacts
      - run:
          name: "Publish Release on GitHub"
          command: |
            go get github.com/tcnksm/ghr
            VERSION=$(my-binary --version)
            ghr -t ${GITHUB_TOKEN} -u ${CIRCLE_PROJECT_USERNAME} -r ${CIRCLE_PROJECT_REPONAME} -c ${CIRCLE_SHA1} -delete ${VERSION} ./artifacts/

CI Builds CircleCI 2.0 example

This is a CircleCI job called publish-github-release that uses a CircleCI Go convenience image. Here's the breakdown:

• Using workspaces, we pull in the binaries for our project from a previous job (not covered in this post).
• This job pulls and compiles ghr via go get (since ghr is written in Go).
• It populates $VERSION with the output of my-binary --version, our example application for this post.
• We then use the ghr command to upload the binaries in the artifacts directory to GitHub.

We can shave a few seconds off of the job above by using the ghr Docker image from CI Builds. It's a lightweight Docker image that already has ghr installed. Here's how the new example config would look:

  publish-github-release:
    docker:
      - image: cibuilds/github:0.10
    steps:
      - attach_workspace:
          at: ./artifacts
      - run:
          name: "Publish Release on GitHub"
          command: |
            VERSION=$(my-binary --version)
            ghr -t ${GITHUB_TOKEN} -u ${CIRCLE_PROJECT_USERNAME} -r ${CIRCLE_PROJECT_REPONAME} -c ${CIRCLE_SHA1} -delete ${VERSION} ./artifacts/

Workflow example

Here's an example of how one of the variations of the above job can be implemented within a Workflow to publish tagged commits to GitHub releases:

workflows:
  version: 2
  main:
    jobs:
      - build:
          filters:
            tags:
              only: /^\d+\.\d+\.\d+$/
      - publish-github-release:
          requires:
            - build
          filters:
            branches:
              ignore: /.*/
            tags:
              only: /^\d+\.\d+\.\d+$/

In this example, we have CircleCI kick off the publish-github-release job when a git tag is pushed. How exactly you choose when to publish a GitHub release is up to you, but here we'll do it with a SemVer-like git tag. We say SemVer-like because the tag regex we're using /^\d+\.\d+\.\d+$/ matches tags such as 1.2.3 but doesn't take into account all of the rules of SemVer (Semantic Versioning).

For the sake of completeness, here's what a complete regex for SemVer would look like according to rgxdb.com:

/(?<=^[Vv]|^)(?:(?<major>(?:0|[1-9](?:(?:0|[1-9])+)*))[.](?<minor>(?:0|[1-9](?:(?:0|[1-9])+)*))[.](?<patch>(?:0|[1-9](?:(?:0|[1-9])+)*))(?:-(?<prerelease>(?:(?:(?:[A-Za-z]|-)(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)?|(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)(?:[A-Za-z]|-)(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)?)|(?:0|[1-9](?:(?:0|[1-9])+)*))(?:[.](?:(?:(?:[A-Za-z]|-)(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)?|(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)(?:[A-Za-z]|-)(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)?)|(?:0|[1-9](?:(?:0|[1-9])+)*)))*))?(?:[+](?<build>(?:(?:(?:[A-Za-z]|-)(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)?|(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)(?:[A-Za-z]|-)(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)?)|(?:(?:0|[1-9])+))(?:[.](?:(?:(?:[A-Za-z]|-)(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)?|(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)(?:[A-Za-z]|-)(?:(?:(?:0|[1-9])|(?:[A-Za-z]|-))+)?)|(?:(?:0|[1-9])+)))*))?)$/