Client Preparation: Merge Request: Conflict Resolver

~Conversation: #551 (closed)

The GitLab conflict resolution code needs to be migrated to Gitaly. In order to do this, the GitLab-CE codebase needs to be prepared for this change, through several refactors:

1. Conflict resolution handling should become contained within the GitLab::Git module

   • It should not have dependencies outside of GitLab::Git
   • It should not have dependencies on services such as Redis, Database etc

2. Conflict resolution needs to be refactored to use a RPC request-response calling style

   • The calling interface should take simple string references to branch names, commit shas, storage and repository path references.
   • The calling interface should not be passed activerecord objects, rugged objects, or other objects
   • The response should return all the information that the caller requires. So, for example, if the caller renders a template that contains the commit message, then this needs to be passed back from the interface. In order words, the caller should not need to instantiate a rugged object in order to obtain information after making the call - everything it needs should be returned by the new conflict resolution handler.
   • The interface should send all the required information up front and should not rely on callback style interfaces to obtain more information during the call

Process

Current

Step 1: Client Preparation (this task):

Step 3: Gitaly Migration (the future):

References

https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/services/merge_requests/conflicts/resolve_service.rb#L9-34

calls

https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/gitlab/conflict/file_collection.rb#L15-26

calls

https://gitlab.com/gitlab-org/gitlab-ce/blob/90f83ca487cb64a5244709994e3220cfca2453d4/app/models/repository.rb#L918-924

Example

This code is a good example of a migration ready git operation.

• It doesn't contain any Rugged or ActiveRecord models in it's method signature or return values.

• It's easy to serialize and deserialize over the wire

• https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14154/diffs#63b1705ba0e09c0aff420d57d5a7912e1fec69e2_861_846