Cross Repository GitHub Action Triggering

Wow what a title.

While developing the reference for our project Basil.js we ran into the following problem. We are lazy and we don’t want to touch the reference each time some new function is added or even worse – we find a type in the JSDoc comments in the source.

I took a look into TravisCI but learned early that the cross repo trigger is not possible. At least out of the box. Again. I’m lazy and I have little time to develop a complex TravisCI script that does somehow use GitHubs API to be triggered.

Some time passed and we did not find a solution. Then out of the blue GitHub announced their actions feature ¹. Wooohooo \o/. Here wee goooo 🎢 …

You will need two repositories. Let’s call the first one trigger and the second one target. The trigger repo represents the source of our project Basil.js. Here we are developing and writing the source of our docs. The target repo holds or documentation. In our case it is the GitHub orgs site repo.

You also will need a Personal Access Token. You can create it here. This token needs to be added as a secret to both repositories². You also will have to activate it in your main.workflow³ interface.

The Trigger Repository

On our trigger we create the following action setup. On push we run the docker container defined under ./action. The only needed application in this container is curl to execute the webhook.

This is .github/main.workflow:

workflow "trigger" {
  on = "push"
  resolves = ["run-it"]
}

action "run-it" {
  uses = "./action"
  secrets = ["PA_TOKEN"]
}

This is the content of action/Dockerfile:

FROM alpine
RUN apk add --no-cache curl
ADD entrypoint.sh /entrypoint.sh
ENTRYPOINT ["/entrypoint.sh"]

This is action/entrypoint.sh with the curl post call:

#!/bin/sh -l
sh -c "curl -XPOST -H \"Accept: \
application/vnd.github.everest-preview+json\"  \
-H \"Content-Type: application/json\" \
-H \"Authorization: token ${PA_TOKEN}\" \
https://api.github.com/repos/fabianmoronzirfas/target/dispatches \
--data '{\"event_type\": \"run-it\"}'"

The Target Repository

This is .github/main.workflow. Currently this is configured to build on the webhook repository_dispatch trigger.

In this example the args and the env values are not used. Just for illustrating the possibility of having them. The repo waits on its webhook to be called and then executes the script in the docker container.

workflow "Build-it on webhook" {
  on = "repository_dispatch"
  resolves = ["execute build"]
}

action "execute build" {
  uses = "./action"
  env = {
    NAME = "fabianmoronzirfas"
  }
  args = "\"This name is set as a env variable: $NAME\""
  secrets = ["PA_TOKEN"]
}

The container has the following dependencies:

• git
• node.js
• npm
• openssh
• bash (optional)

This is the content of action/Dockerfile:

FROM alpine
ADD entrypoint.sh /entrypoint.sh
RUN apk --update add --no-cache bash nodejs nodejs-npm git openssh
ENTRYPOINT ["/entrypoint.sh"]

And this is the script that does the execution. Fist we output some infos to see if the install worked. The important part is the npm run build call. It is a Node.js script that creates a file within the container. It is very simple in our case just a require('fs').writeFileSync('./out-date', JSON.stringify(new Date())) to have some output. Then it adds this file with git and uses the Personal Access Token to push to the repo via https.

This is action/entrypoint.sh:

#!/bin/sh -l
sh -c "echo 'in entrypoint.sh'"
sh -c "echo 'NODE version:' $(node -v)"
sh -c "echo 'NPM version:' $(npm -v)"
sh -c "echo 'GIT version:' $(git --version)"
sh -c "echo 'output of pwd:' && pwd"
sh -c "echo 'output of ls:' && ls"
sh -c "echo 'these are arguments set to the workflow' && echo ${*}"
sh -c "cd action && npm test"
sh -c "cd action && npm run build"
sh -c "cd action && echo 'output of ls:' && ls"
sh -c "git config --global user.email 'fabian.moron.zirfas@gmail.com'"
sh -c "git config --global user.name 'me-as-a-bot'"
sh -c "echo 'git status' && git status"
sh -c "git add ."
sh -c "git commit -m 'added file'"
sh -c "git push https://${PA_TOKEN}@github.com/fabianmoronzirfas/target.git"

As soon as GitHub Actions are out of beta I will make these repos public so you can take a look at the source.