Thanks. I’ve accepted it as a sollution.

Even if it doesn’t really work for my specific usecase, it does seem like a valid way to solve my question.

I have 1 library that is used by about 10 different repositories. And I don’t want to add knowledge about those external repositories to my main library repository. My home grown CI solution currently allows this “watch link”, but I understand that it’s a bit of an odd usecase.

Is it possible to go the other way.

If my repository depends on 4 other repos can an action be triggered if one of them has a commit action (to the master for example.)?

This is pretty important for our CI across an SDK which is split into various modules across different repos. It’s something that’s supported in Jenkins. Hopefully this will be functionality that arrives at some point.

We also don’t want to hardcode details about consumer modules in our library modules. One solution could be to use a webhook, then from the webhook invoke the workflows using repo dispatch. Feels like quite a bit of effort to set this up though and dependency context would need sorted somewhere else too.

Another option could be to have an intermediate repo which holds workflows which hold teh dependency contexts, so the lib workflow simply uses repository dispatch on a workflow in the intermediate repo. That workflow then does a repo dispatch on the required workflows in other repos. If dependencies change, then they can be updated in one place.

How can I use it for two repositories on an organization?

As far as I understand, this still uses the default repo-scoped GITHUB_TOKEN so you need to pass your own token if you want to access a different repository: GitHub - actions/github-script: Write workflows scripting the GitHub API in JavaScript

Also worth noting that the documentation link to the right area is https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#repository_dispatch

Hello

have you found a simple Solution?

The Problem is simple and a default situation nearly every developer is in.

Java + maven Example
1 Repo with a lib => Version 0.1.0-SNAPSHOT
1 Repo with the app =>depends on repo lib => 0.1.0-SNAPSHOT
both repos are own be the same developer/company

1 Developer commits something to the lib => i want to rebuild the app fully automated. without knowledge in the lib which app uses this lib.

any idea? i havent found some solution for this use case

Appreciate you taking the time to inform us. Definitely takes a lot of trial and error.

I had a lot of back end forth and this is what worked for me:

We have a backend repo with a GitHub Action to pull the frontend, build node, authenticate to gcloud, and deploy to google app engine. I wanted to create an Action in my frontend that when someone merges/pushes to development branch we simply tell the backend to go pull the frontend development branch fresh and try to deploy.
The Action in the backend also runs on push to development branch on that side as well. That is how our CI is setup.

After a lot of back and forth this is what worked for me:

name: Trigger Backend Action to Deploy

on:
  push:
    branches: 
      - deployment

jobs:
  send-request-to-backend:
    runs-on: ubuntu-latest
    steps:
      - name: Deploy
        run: |
          curl -X POST 'https://api.github.com/repos/{COMPANY}/{BACKEND_REPO}/actions/workflows/ci-development.yml/dispatches' \
          -H 'Accept: application/vnd.github.everest-preview+json' \
          -H 'Authorization: Bearer ${{ secrets.RUN_BACKEND_ACTION_TO_DEPLOY }}' \
          -d '{"ref":"development"}'

Notes:

• The ref development was required as the branch on which to run this even though both scripts explicitly refer to development branches in both repos, but that -d was required. I didn't try it with an empty value
• I had to put single quotes around the URL or else it would throw an error that it wasn't found
• ci-development.yml in the URL is the backend github action

My org has created https://github.com/marketplace/webhook-actions to allow for dispatching across repositories without the use of PATs. Currently we can only offer a free plan until we reach 100 installations.

so i came up with a horrible way to do this. set up a webhook in discord to post to a private channel when the repo has the desired trigger. then have a bot watch the channel for messages and when there's a message it will trigger your repo. yes i know this is horrible

This is how I got the repository_dispatch (not workflow_dispatch) approach mentioned in the answer to work.
Workflow in my-org/target-repo:

# file: target.yml

name: Gets called

on:
  repository_dispatch:
    types: [bcd_release]

jobs:
  dostuff:
    runs-on: ubuntu-latest
    steps:
      - name: "do stuff"
        env:
          VERSION: ${{ github.event.client_payload.version }}
        run: |
          echo BCD version $VERSION released!

Create a PAT in your user account settings. Use "Fine-grained tokens (beta)", select the target-repo, give read-write access to "Content" category, copy the token code and put it in a secret(DISPATCH_PAT) in my-org/source-repo.

Workflow in my-org/source-repo:

#file: source.yml

name: Release BCD

# I am triggering this manually so using 'workflow_dispatch'
on:
  workflow_dispatch

jobs:
  release:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/github-script@v6
      with:
        github-token: ${{ secrets.DISPATCH_PAT }}
        script: |
          const result = await github.rest.repos.createDispatchEvent({
            owner: 'my-org',
            repo: 'target-repo',
            event_type: 'bcd_release',
            client_payload: {"version": "v5.3.10"}
          })
          console.log(result);

Here is our working live implementation:

• Source repo, mdn/browser-compat-data, makes a repository_dispatch request named bcd_release after the package is published to NPM.
• In target repo, mdn/bcd-utils, multiple workflows gets triggered by the bcd_release event. For example, Prod Build - API and Prod Build - Updates workflows.

How can I apply this to a pair of repositories within an organization?

Not exactly a solution to the requested, but there is always the option to schedule the running of a workflow in your Application repo to check for changes in the Library repo, and when it finds changes, perform a build!

I use this approach on a couple of repositories of mine, specifically:

• https://github.com/pedrolamas/docker-mainsail/blob/5d355784876de54a75af5733c80545c08898b1b1/.github/workflows/main.yml#L5
• https://github.com/pedrolamas/docker-klipper-simulavr/blob/348be296310f4e83d1f7de804a79c89afe4c49d6/.github/workflows/main.yml#L5

In both cases, I check the latest commit to the referenced repo, calculate a hash of it, and check if I have a docker container with that hash; if I do, the workflow ends, but if such image does not exist, it will perform the build action to the end!