[feature] Multi-repo workflow

[Ranger-X]

multi-repo CI workflow differs from basic CI (which in templates) in the following key aspects:

• In multi-repo workflow we can push to dev and prod registries separately with their own rules (see jobs/multi-repo and/or examples/multi-repo-module.gitlab-ci.yml for example jobs).
• All werf's caches and other artifacts (from build stage) are stored in Gitlab's module's registry by default. And only final images are pushed to the dev/prod registries. So, even in dev-registry there should be no "build-time garbage" and/or some "extra" images/layers for each module.

[KraMorK]

only, when and rules don't work well together. If we implement rules, then it's better to get rid of when without rules in the job and only in these jobs.

[Ranger-X]

In multi-repo templates (templates/multi-repo/*.yml) I use rules everywhere. Do you mean get rid of only in simple templates (templates/*.yml)?

[KraMorK]

#in gitlab-ci it is better to use docker-executor, separately prepare the image and call it. this will reduce the busy time of runners, add isolation between jobs, reduce the number of used dependencies (possible points of failure) and increase security. but perhaps they will not agree with me

[Ranger-X]

I agree about a separate image for docker/kubernetes-executor.
But minor/patch versions of Werf/DMT come out quite often and maintaining a separate CI-image can be "more expensive" in terms of time than installing current versions of tools every time pipeline is launched. 😇

I can also be wrong with my conclusions. 😅