introduce include to load sub-compose projects as dependencies

[ndeloof]

This adds support for include attribute introduced in the compose-specification by compose-spec/compose-spec#363

This supports including compose sub-projects, comparable to language dependency management

usage:

include:
   - ../commons/compose.yaml
   - ../another-project/compose.yaml

services:
   foo:
      depends_on:
         - imported-service

required projects are resolved based on their own project directory to avoid relative path hell.

[milas]

LGTM

[glours]

Sounds good to me, you just need to fix the conflict before merging

[glours]

nit: can't we use generics here?

[ndeloof]

this signature isn't a "lack of generics": those manage the parsed yaml nodes, which are actual interface{}

[glours]

nit: could also be apply to the following if !opts. blocks

Suggested change

	err := ResolveRelativePaths(project)
	if err != nil {
	return nil, err
	}
	if err := ResolveRelativePaths(project); err != nil {
	return nil, err
	}

[ndeloof]

I personally consider those to have lower readability for the tiny benefit of a single line being saved

especially as the "long" syntax is displayed in my goland IDE as a single "error handling" line:

        err := ResolveRelativePaths(project)
		if err != nil : nil, err ⮑

[glours]

As you wish, I don't have a strong opinion about this 😉

[glours]

nit: new line

[vasilvestre]

Could it work with URL later ?

[ndeloof]

@vasilvestre this is indeed something we consider for future, also see compose-spec/compose-spec#288

[VladaPetrovic]

The functionality to include the remote file would be a great addition to this feature 🚀
It was already proposed in the original idea

for example:

include:
https://localhost:8000/some-service/compose.yaml
...

We could leverage this feature to re-use Compose files across teams. Currently, we’re cloning an additional repository solely to include another Compose file, which feels a bit cumbersome. 🤔

The mentioned compose-spec/compose-spec#288 seems like a broader feature with a much larger scope. While it could also address this problem, it approaches it from a different perspective.