Gitlab merge request are broken

[koushyk]

Checklist

• [x] I've searched the issue queue to verify this is not a duplicate bug report.
• [x] I've included steps to reproduce the bug.
• [x] I've pasted the output of kargo version.
• [ ] I've pasted logs, if applicable.

Description

When promoting a fright to stage which has merge request creation enabled I'm getting an error

error executing Git-based promotion mechanisms: error executing Kargo Render promotion mechanism: error preparing PR branch "https://<gitlab_url>/deploy/service.git": error checking out branch "master\n" from repo "https://<gitlab_url>//deploy/service.git": error executing cmd [/usr/bin/git checkout master --]: fatal: invalid reference: master

but for stages without merge request features promotions are working as they should.

Screenshots

Steps to Reproduce

1. Create a warehouse with helm and image in different repositories.
2. Create stage

   kind: Warehouse
   spec:
   freightCreationPolicy: Automatic
   interval: 5m0s
   subscriptions:
   - git:
       branch: master
       commitSelectionStrategy: NewestFromBranch
       discoveryLimit: 20
       includePaths:
         - service
       repoURL: https://<gitlab_url>/service.git
       strictSemvers: true
   - image:
       allowTags: ^[^sha256].*$
       discoveryLimit: 20
       gitRepoURL: https://<gitlab_url>/service.git
       imageSelectionStrategy: NewestBuild
       repoURL: <registry_url>/service
       strictSemvers: true
   ---
   apiVersion: kargo.akuity.io/v1alpha1
   kind: Stage
   metadata:
   name: <stage-name>
   spec:
   promotionMechanisms:
   argoCDAppUpdates:
     - appName: <argocd_app_name>
   gitRepoUpdates:
     - render: {}
       repoURL: https://<gitlab_url>/service.git
       writeBranch: env/<env-name>/<service-name>
   requestedFreight:
   - origin:
       kind: Warehouse
       name: <service-name>-wh
     sources:
       direct: true
   shard: stage
   ---
   apiVersion: kargo.akuity.io/v1alpha1 
   kind: Stage
   metadata:
   name: <stage-name>
   spec:
   promotionMechanisms:
   gitRepoUpdates:
     - render: {}
       repoURL: https://<gitlab_url>/deploy/service.git
       writeBranch: env/<env>/<service-name>
       pullRequest:
         gitlab: {}
   requestedFreight:
   - origin:
       kind: Warehouse
       name: <service-name>-wh
     sources:
       stages:
         - <stage-name>

3. Promote fright

Version

{
  "Version": "v0.9.1",
  "BuildDate": "2024-10-11T04:59:22Z",
  "GitCommit": "a1a43b7c59780e726b6438fd41cc74597dd442b6",
  "GitTreeDirty": false,
  "GoVersion": "go1.23.2",
  "Compiler": "gc",
  "Platform": "linux/amd64"
}

Logs

Paste any relevant application logs here.

[krancour]

@koushyk is <gitlab_url> on gitlab.com or self-hosted GitLab?

[koushyk]

@krancour self-hosted

[krancour]

I'm perplexed by why it's attempting to checkout master in the first place.

It has reason to check out a specific commit from master as well as the env/<env>/<service-name> branch you intend to write to, but no reason that I can spot that master should be checked out here.

Would you possibly be able to enable debug logging and see if there's any useful details about what exactly it was doing leading up to this?

Edit: These legacy promotion mechanisms were deprecated in v0.9.0 and will be fully removed in v1.0.0. I suspect the issue here isn't with the gitlab bits, but with the more general git bits preceding the opening of an MR. It would also be interesting to see if the equivalent workflow using a promotion template is prone to the same issue or not.

[koushyk]

I've updated manifests to promotion templates and merge requests are creating fine, so I have to switch to promotion templates anyway.

[krancour]

Thank you for doing that. It's a good data point. While we're not investing in further development of the old promotion mechanisms, we still plan to fix bugs in them for some time so that we can extend the life of v0.9.x while people make the transition to the promotion templates. This has really helped to narrow down where I need to be looking. Thanks again.