Implements the `pre_start` service field introduced in
compose-spec/compose-spec#647: an ordered list
of init containers run to completion before the service container
starts. Each step runs in its own ephemeral container; a non-zero exit
fails the bring-up of the service and its dependents.

Compose-go owns parsing, validation via JSON schema, and image
inheritance: when a pre_start hook omits `image`, it is normalized
to the parent service's image. Volume/network inheritance and the
runtime execution stay with docker/compose.

Signed-off-by: Guillaume Lours <[email protected]>

Implements the `pre_start` service field introduced in
compose-spec/compose-spec#647: an ordered list
of init containers run to completion before the service container
starts. Each step runs in its own ephemeral container; a non-zero exit
fails the bring-up of the service and its dependents.

Compose-go owns parsing, validation via JSON schema, and image
inheritance: when a pre_start hook omits `image`, it is normalized
to the parent service's image. Volume/network inheritance and the
runtime execution stay with docker/compose.

Signed-off-by: Guillaume Lours <[email protected]>

Implements the `pre_start` service field introduced in
compose-spec/compose-spec#647: an ordered list
of init containers run to completion before the service container
starts. Each step runs in its own ephemeral container; a non-zero exit
fails the bring-up of the service and its dependents.

Compose-go owns parsing, validation via JSON schema, and image
inheritance: when a pre_start hook omits `image`, it is normalized
to the parent service's image. Volume/network inheritance and the
runtime execution stay with docker/compose.

Signed-off-by: Guillaume Lours <[email protected]>

<!--Delete sections as needed -->

## Description

As per docker/compose#13862 and
compose-spec/compose-spec#647

## Related issues or tickets

<!-- Related issues, pull requests, or Jira tickets -->

## Reviews

<!-- Notes for reviewers here -->
<!-- List applicable reviews (optionally @tag reviewers) -->

- [ ] Technical review
- [ ] Editorial review
- [ ] Product review

---------

Co-authored-by: Guillaume Lours <[email protected]>

… triggers

Follow-up to #647, addressing gaps identified while implementing the hook:

- state explicitly that pre_start steps only run once the service's
  depends_on conditions have been satisfied
- define per_replica: true semantics: one run per replica, tied to that
  replica's mounts and start; declared order preserved per replica, runs
  for distinct replicas may execute concurrently; a failed run prevents
  that replica from starting and fails the service bring-up
- state that per_replica: false on a scaled service is not an error when
  per-instance mounts exist; such steps simply run without access to them
- define "definition changes" (any attribute) and "service is recreated"
  (container recreation: config change, forced recreate) as re-run triggers
- replace the tmpfs example on per_replica: volume sharing relies on
  volumes_from, which does not propagate tmpfs mounts
- fix broken post_start link in the pre_stop section

Signed-off-by: Guillaume Lours <[email protected]>