Trigger GitHub actions if push in another repo - github

Question

In one of my repos (repo A), there is a script that gets the content of a file on another repo (repo B, not one of mine). Therefore, I would like to trigger a GitHub action on repo A each time there's a push on repo B. I didn't see this case on GitHub actions trigger documentation, is this possible?

Answer 1

You can execute each day a script with cron in order to start or not your workflow. A script can read easily the date of last commit of another repository.
Detect when the last commit is less than a day old
With this script, the exit code is 0, only if the last commit is less than a day old.
#!/bin/bash
exit $(curl -s https://api.github.com/repos/wikimedia/mediawiki/commits/REL1_36 | jq -r "((now - (.commit.author.date | fromdateiso8601) ) / (60*60*24) | trunc)")
Execute the script with cron each day
name: trigger
on:
schedule:
- cron: '30 5 * * *'
workflow_dispatch:
jobs:
check:
runs-on: ubuntu-latest
steps:
- name: Checkout
uses: actions/checkout#v2
- run: ./isUpdated.sh
Start your workflow when a new commit exists since yesterday
name: Your workflow
on:
workflow_run:
workflows: ["trigger"]
types: [completed]
workflow_dispatch:
jobs:
check:
runs-on: ubuntu-latest
if: ${{ github.event.workflow_run.conclusion == 'success' }}
steps:
- name: Checkout
uses: actions/checkout#v2
- run: echo ok

Answer 2

edit: this won't work since OP doesn't have push access to repo B
I think that you might be able to get what you want by using the repository_dispatch event. This essentially triggers the workflow when an endpoint is pinged with the correct payload.
From the documentation:
To trigger the custom repository_dispatch webhook event, you must send a POST request to a GitHub API endpoint and provide an event_type name to describe the activity type. To trigger a workflow run, you must also configure your workflow to use the repository_dispatch event.
My best guess is that your desired solution can be achieved by creating 2 workflows: 1 in Repo A that runs on: repository_dispatch, and 1 in Repo B that runs on: push and contains a step that hits Repo A's API (e.g. using curl). This would give you the following events:
You push to Repo B.
Repo B's on: push workflow is triggered, and the step that hits Repo A's API endpoint (e.g. using curl) is run.
Repo A's API endpoint receives the payload and the on: repository_dispatch workflow is triggered.