Adds the option to watch a different repo

[ribalba]

As I can see the case quite often, that we want to monitor a repo and then execute a usage scenario from another repo here is a first idea how to do this.

@ArneTR what do you think about this implementation as it is your code.

I still need to write the migration and do tests. But didn't want to spend too much time on this as I am assuming a change.

[greptile-apps]

Skipped: This PR does not contain any of your configured keywords: (greptile-this-will-never-be-only-manual)

[ArneTR]

Thanks for checking in early here.

I feel this is not something that makes any sense in GMT as it incresases the complexity of how to execute runs even more.

Acually I am not even really happy with the way that GMT currently can monitor for tag / commit changes.
It is somethingthat the tool should have no knowledge of IMHO.

I would argue this is best done in an external solution and not in GMT itself.

Having code that checks a repository, which then has a linked repository, which then needs to be checked ... that feels like too much.
Also I see edge cases not covered. Your code does now NOT execute when the nextcloud-runner repo gets changed. but only when the linked repo does. But is not what we want that if ANY gets changed we want to monitor. But then I can think of users that do want to trigger a RUN only when the BASE repo gets changed, but not the linked one and so on .... I think this goes to far.

Also it would be nice if this "external service" understands GitHub Webhooks directly and can emit a GMT run from there ...

Let's phone tomorrow about this

[ArneTR]

As discussed this functionality is planned to rather have external to GMT