Support creating workspaces from Drupal GitLab issue forks and associated merge requests

[gxleano]

Problem

From Drupal Slack https://drupal.slack.com/archives/C5TQRQZRR/p1781693360466449

When creating a new workspace from a GitLab issue number, Coder DDEV incorrectly reports that no issue fork exists, even though the issue fork has already been created and push access has been granted.

Steps to reproduce

1. Follow the permissions and setup described in the Drupal issue notes:
   https://start.coder.ddev.com/drupal-issue
2. Enter the GitLab issue number 3591879 in the workspace loader.
3. Attempt to create a workspace.

Actual result

The following error is displayed:

No issue fork exists for #3591879 yet. To work on this issue, visit the issue page on drupal.org and click "Get push access" to create a fork, then come back here.

Expected result

The workspace should be created successfully because an issue fork already exists and push access has already been granted.

For example, the issue fork exists at:

https://git.drupalcode.org/issue/ui_icons-3591879

and contains the issue branch:

3591879-make-the-ui-icon-fieldwidget-editable-as-a-drupal-canvas-component-input

Proposed enhancement

When a GitLab issue number is entered, Coder DDEV should be able to:

1. Locate the corresponding GitLab issue fork.
2. Detect any associated Merge Request(s).
3. Create the workspace from the issue branch or MR branch automatically.

For example:

• Issue fork:
  https://git.drupalcode.org/issue/ui_icons-3591879
• Merge Request:
  https://git.drupalcode.org/project/ui_icons/-/merge_requests/99

In this example, creating a workspace for issue 3591879 should result in a workspace that already contains the code from MR !99, allowing contributors to review, test, and continue work immediately without manually checking out the MR branch.

Benefits

• Better support for GitLab-native Drupal contribution workflows.
• Faster onboarding for contributors reviewing existing work.
• Reduced confusion caused by Drupal.org-specific error messages when working with GitLab issues.
• Consistent workspace creation experience regardless of whether the issue is hosted on Drupal.org or GitLab.

[rfay]

@gxleano do you know if issue numbers still remain unique through the Drupal ecosystem ?

[gxleano]

@rfay I have asked to @fjgarlin who is in charge on the Gitlab migration and he told me that they are not unique globally.

Different modules can have the same IID, but it would be unique per module. So, we could just try to make it works with module-issue_number:

ui_icons-3591879

[rfay]

Probably we just have to insist on the full link going forward.