HPCC-35885 Provide upmergeability test workflow

[jpmcmu]

• Migrated HPCC4J upmerge test workflow to HPCC project

Signed-off-by: James McMullan James.McMullan@lexisnexis.com

Type of change:

• This change is a bug fix (non-breaking change which fixes an issue).
• This change is a new feature (non-breaking change which adds functionality).
• This change improves the code (refactor or other change that does not change the functionality)
• This change fixes warnings (the fix does not alter the functionality or the generated code)
• This change is a breaking change (fix or feature that will cause existing behavior to change).
• This change alters the query API (existing queries will have to be recompiled)

Checklist:

• My code follows the code style of this project.
  • My code does not create any new warnings from compiler, build system, or lint.
• The commit message is properly formatted and free of typos.
  • The commit message title makes sense in a changelog, by itself.
  • The commit is signed.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly, or...
  • I have created a JIRA ticket to update the documentation.
  • Any new interfaces or exported functions are appropriately commented.
• I have read the CONTRIBUTORS document.
• The change has been fully tested:
  • I have added tests to cover my changes.
  • All new and existing tests passed.
  • I have checked that this change does not introduce memory leaks.
  • I have used Valgrind or similar tools to check for potential issues.
• I have given due consideration to all of the following potential concerns:
  • Scalability
  • Performance
  • Security
  • Thread-safety
  • Cloud-compatibility
  • Premature optimization
  • Existing deployed queries will not be broken
  • This change fixes the problem, not just the symptom
  • The target branch of this pull request is appropriate for such a change.
• There are no similar instances of the same problem that should be addressed
  • I have addressed them here
  • I have raised JIRA issues to address them separately
• This is a user interface / front-end modification
  • I have tested my changes in multiple modern browsers
  • The component(s) render as expected

Smoketest:

• Send notifications about my Pull Request position in Smoketest queue.
• Test my draft Pull Request.

Testing:

[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-35885

Jirabot Action Result:
Workflow Transition To: Merge Pending
Updated PR

[Copilot]

Pull request overview

Adds a new GitHub Actions workflow intended to validate “upmergeability” of PRs targeting candidate branches in the HPCC Platform repo.

Changes:

• Introduces an upmerge-test workflow triggered on PR open/reopen against candidate-* branches.
• Computes a list of “upmerge target” branches from git tags and checks for merge conflicts via git merge-tree.
• Uploads JSON/text artifacts and fails the workflow when conflicts are detected.

[jpmcmu]

Examples of upmerge comments:
jpmcmu#17

Successful workflow run:
https://github.com/hpcc-systems/HPCC-Platform/actions/runs/22309278990

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

[ghalliday]

One question. Main proof will be enabling and looking at the results.

[ghalliday]

Should this unconditionally add "master"?