fix: detect credential changes in project mirror URL

Relates to issue #6403 (closed)

Changes

This MR fixes the credential diff detection issue in the gitlab_project_push_mirror resource where changes to only the username/password in the mirror URL were not being detected by Terraform.

Modified Files

1. internal/provider/resource_gitlab_project_push_mirror.go

• Lines 26-31: Added ResourceWithModifyPlan interface assertion to ensure ModifyPlan is recognized by Terraform framework
• Lines 88-147: Completely rewrote the ModifyPlan logic:
  • Detects if URLs contain credentials (url.User != nil)
  • When credentials are present: Compares URLs WITHOUT redaction, allowing credential-only changes to be detected
  • When credentials are present: Adds deprecation warning about embedding credentials in URLs
  • When NO credentials are present: Uses existing redaction logic for backward compatibility
  • Properly marks URL for replacement when differences are detected

2. internal/provider/resource_gitlab_project_push_mirror_test.go

Added three comprehensive test cases:

• TestAccGitlabProjectMirror_credentialChange (Lines 488-530): Tests that changing credentials in URL triggers resource replacement
• TestAccGitlabProjectMirror_credentialChangeWarning (Lines 531-561): Verifies deprecation warning is emitted when credentials are embedded in URLs
• TestAccGitlabProjectMirror_urlChangeWithoutCredentials (Lines 562-618): Ensures backward compatibility for URLs without credentials

Key Features

1. Credential Change Detection: Resource now properly detects when only username/password in the URL are modified, triggering resource replacement
2. Deprecation Warning: Users are warned when embedding credentials in URLs with guidance toward future best practices
3. Backward Compatibility: URLs without credentials continue to work exactly as before
4. Comprehensive Test Coverage: Three new tests cover credential changes, warning emission, and backward compatibility

Testing

Before merging, run:

make reviewable

For acceptance testing:

unset GITLAB_TOKEN && make testacc-up
unset GITLAB_TOKEN && make testacc RUN=TestAccGitlabProjectMirror_credentialChange
unset GITLAB_TOKEN && make testacc RUN=TestAccGitlabProjectMirror_credentialChangeWarning
unset GITLAB_TOKEN && make testacc RUN=TestAccGitlabProjectMirror_urlChangeWithoutCredentials
unset GITLAB_TOKEN && make testacc-down