[piped] Create a new pull request feature

[sivchari]

What would you like to be added:

Now, event-watcher of Piped's feature doesn't create a new pull request, when it pushes a new commit to repository. But a number of repository prohibits the push to default branch. So, I propose the new feature to create a pull request. This feature is optional, so if someone doesn't want this feature, they can ignore it. But if this idea is accepted, we will think a lot of things (e.g. About /pkg/git). So I want to discuss about this feature is needed or not.

Why is this needed:

[nnnkkk7]

How about implementing it this way?

Overview
Add an optional flag to Git in the following configuration to indicate whether or not to create a new branch.
https://pipecd.dev/docs/user-guide/managing-piped/configuration-reference/#git

Details

• This filed is defined as enableNewBranch and the type is bool.
• The argument of newBranch in the CommitChanges method is currently passed a fixed false, so we will pass enableNewBranch in config.
  https://github.com/pipe-cd/pipecd/blob/master/pkg/app/piped/eventwatcher/eventwatcher.go#L642
• In the CommitChanges method, if newBranch is true, Git client checkouts a new branch. So we should need a some kind of branch name to checkout.
  Therefore, if enableNewBranch is true, Git client makes a new branch named {eventName}-{uuid} (uuid is generated by already depended google/uuid lib).
  https://github.com/pipe-cd/pipecd/blob/master/pkg/app/piped/eventwatcher/eventwatcher.go#L596

If ok, I would like to create a new PR related with this. wdyt ?

[sivchari]

I agree with your opinion, but I would like to discuss if the field name is optimal with @nnnkkk7 and @khanhtc1202 .
And do you think where it's better that uuid is generated ? I think uuid should be generated by a uuid-generator-client which piped-agent newly has. That why, Git client has no side-effect to test.

[nnnkkk7]

@sivchari @khanhtc1202
Thanks!
I think it is better from a testing point of view to create a uuid-generator-client, but currently other parts of the program also directly use google/uuid methods, so I would like to make it a separate scope for this Issue. And uuid-generator-client would make it easier to test other parts, so it would be good to set up such an issue.

[nnnkkk7]

I created PR about this issue.
#4395

[khanhtc1202]

@nnnkkk7 @sivchari Thanks so much for your contribution 🙌
Sorry for my late on design comments, the current implementation is acceptable. But there is a bit "UX kind" problem here I want to make it clear.

I think the git configuration (ref https://pipecd.dev/docs/user-guide/managing-piped/configuration-reference/#git) currently only focuses on configuring git auth to use the git command, not how the git command should be used.

If we enable this configuration in piped.spec.git, then at the time when users configure for their piped, they have to decide do they want that config or not, and they may don't even know about the event watcher. That's why I think we should move this configuration closed to event watcher related part, which should be

In case of using event watcher independent configuration (ref: https://pipecd.dev/docs/user-guide/event-watcher/#use-the-pipe-directory)

apiVersion: pipecd.dev/v1beta1
kind: EventWatcher
spec:
  events:
    - name: helloworld-image-update
      createMergeRequest: true
      replacements:
        - file: helloworld/deployment.yaml
          yamlField: $.spec.template.spec.containers[0].image

In case of using application configuration config

apiVersion: pipecd.dev/v1beta1
kind: KubernetesApp
spec:
  name: helloworld
  eventWatcher:
    - matcher:
        name: helloworld-image-update
      handler:
        type: GIT_UPDATE
        config:
          createMergeRequest: true
          replacements:
            - file: deployment.yaml
              yamlField: $.spec.template.spec.containers[0].image

wdyt?

[khanhtc1202]

Also, the implementation at PR #4395 only commits the change in a new branch, I think we should make the merge request from that branch to the piped watching branch (main/master by default), or users can't complete their CI -> CD connection if they don't create the PR from the piped submitted branch manually.

[nnnkkk7]

@khanhtc1202
Thanks so much!!!

That's why I think we should move this configuration closed to event watcher related part

I think so too. so, fix this in this commit .
And I renamed flag.
add createPullRequest flag to event watcher config instead of git config)

[nnnkkk7]

Also, the implementation at PR #4395 only commits the change in a new branch, I think we should make the merge request from that branch to the piped watching branch (main/master by default)

Thanks！
I added Push method after commit in push commit if the branch is new in event watcher PR, but should I add pullrequest method instead of just pushing? If so, would it be appropriate to create a CreatePullRequest method in pipecd/pkg/git/repo.go?

[nnnkkk7]

Also, In the current implementation of pipecd/pkg/git/repo.go, we can't do more than use git command ,for example git push, git commit.
To create a pullrequest, I think we need to replace it with an implementation like

1. Use GitHub API
2. Use GitHub API client Library like google/go-github

Would you have any other ideas?

[khanhtc1202]

@nnnkkk7 Thanks for your investigation 👍

You're right! The current implementation of the pipecd git package does not allow us to make pull requests 😢 We may have to move from using git cmd to using packages like google/go-github to make it programmable.

Let's review and merge the current createPullRequest configuration (aka. #4395) first, then create a separate one for automatically creating pull requests, since we have to change the implementation of the git package and it affects widely 😓

Btw, would you like to practice on that "move from git cmd to google/go-github" ? 😄

[khanhtc1202]

Btw, I just realize that your 2 suggestions both only work with GitHub while pipecd needs to support overall git services (including Bitbucket, GitLab, etc) 😓 We have further investigation for the "auto-create pull request" feature 🤔