Commentary - Update a GitHub comment

This is a small demo that will either create a new comment or update an existing comment on a pull request in GitHub.

I got the idea from Ben Limmer, but I did it in Go.

This seemed like a good way to test how fast the various methods of running GitHub actions authored in Go would be. My theory was that npm had an unfair advantage as it was already baked into the standard runner OS, but (SPOILER) I was wrong!

GitHub Actions - Many Ways to Go!

Although a GitHub Action Ubuntu Runner comes with scripting languages like Bash, NodeJS, Python, etc. it doesn't come with Go 😞. Maintaining code is enough work in a single language without having to also maintain tooling written in a different language, with a different ecosystem. As a result, achieving quick feedback via GitHub Actions written in Go, is all about minimizing data transfer size in order to execute your written-in-Go step with as little wasted setup time as possible.

So to execute GitHub Action steps written in Go, I'm aware of these possibilities:

1. Setup Go in the action, and then just shell out and go run main.go
2. package the Go using npm and further tweaked like this (private or public npm registry as you please)
3. package your Go as a docker container (private or public registry)
4. attach pre-built Go artifacts to a GitHub release and YOLO it (download and execute artifact via shell)
5. attach pre-built Go artifacts to a GitHub release and run those using JS wrappers

I have started to add all these methods to this demo repository to see how they perform. So far I'm done with the first 4, but I imagine the Node wrapper would be the same as the YOLO Bash one if the node script has no need to install npm dependencies.

Which Runner	Elapsed	Download Size
YOLOCommenter	3s	2.92 MB
DockerCommenter	4s	10 MB
NodeCommenter	6s	41 MB
GoRunCommenter	25s	134 MB

The overhead of having to download a Go environment makes go run main.go the slowest, but if your action needs the Go tools anyway, maybe that doesn't add anything. go run main.go is certainly the simplest and easiest to maintain.

You can also use the actions/cache@v2 or (actions-go/toolkit/cache in Go ) to further reduce subsequent startup time in all these cases.

Running as a GitHub Action

There are several environment variables that this needs.

• COMMENTARY_ACTION_TYPE - you can have multiple actions all racing without stepping on each other
• GITHUB_TOKEN - This should be a secret, but is the personal access token of the service account (or your real GitHub account)
• GITHUB_REPOSITORY - Set by GitHub as an owner/repo
• GITHUB_REPOSITORY_OWNER - Set by GitHub as owner
• GITHUB_BASE_REF - Set by GitHub as main
• GITHUB_HEAD_REF - Set by Github to be the branch name, e.g. mybranch
• GITHUB_REF_NAME - Set by Github, for example, 1/merge
• GITHUB_SHA - Set by GitHub as the commit sha1, and used to look up the PR.

Publishing your Go to ... NPM?

After you (er... me?) cut a new release, you (I?) need to increment the package.json version to match, and then run npm publish. If you get a 404, you might need to npm login again.

This Go-published-to-NPM idea was pioneered by Sanath Kumar Ramesh and further tweaked like this.

My silly npm package is commentary-cli has a 39.44 MiB tar ball.

Publishing to Docker

After you cut a new release, you need to push to Docker Hub. There's a handy ko.sh script that will do it for you (er... me?) until I Go-ify it into the magefile.go.

This uses the excellent google/ko to make a fairly small 10 MB image over here

YOLO style shell script to Run from release binary

Really shell code should only be used for boot-strapping to something sane (like Go), so that's exactly what I am doing here.

Downloading a tar.gz file from the latest release, extracting just the executable binary, running the executable is just complicated enough that I don't know how to do it in a short, one line shell script. (I imagine there's a trick to do it)

The installation instructions for a lot of things (e.g. homebrew) have you download and execute a shell script, which seems wildly insecure, so I've heard it referred to it as "YOLO" style installation ("You Only Live Once").

There's a script ./download-extract-execute-artifact.sh that downloads, extracts, and executes the binary artifact.

There's also a more complicated version of that in ./godownloader.sh which is generated by godownloader.

Mage

Instead of make and Makefile, I used mage and made a magefile.

If you do brew install mage then you can run here:

• mage -v run - will run the webserver by doing go run main.go
• mage generate - will re-generate the genqlient code by doing go generate ./...
• mage install - will build and install the commentary application binary
• mage release <v0.?.0> - will generate a new release using Go releaser

Or just run the go commands by hand.

Stuff inside Commentary

I use genqlient to communicate with the GitHub GraphQL API. I used Cobra to scaffold out the cli. I use Mage for task automation.

More GitHub Action in Go reading

I mean to go back and read more of this:

• https://github.com/embano1/ci-demo-app/blob/main/DETAILS.md
• sethvargo/go-githubactions - Go SDK for GitHub Actions
• actions-go/toolkit - Go SDK for GitHub Actions
• Run your GitHub Actions locally with Act
• ChristopherHX/github-act-runner as self-hosted runner
• rhysd/actionlint