Improve Phabricator base-commit resolution

[suhaibmujahid]

Fixes #6415

[Copilot]

Pull request overview

Improves Phabricator base-commit expansion so follow-up runs can reliably resolve abbreviated base commits to full fetchable hashes, even when the commit appears mirrored across multiple repositories and Phabricator doesn’t populate identifierMap.

Changes:

• Enhance PhabricatorClient.resolve_commit() to fall back to a unique prefix match across diffusion.querycommits results when identifierMap is empty.
• Add client tests covering mirrored commits, non-expansion matches, and ambiguous abbreviations.
• Emit a broker warning when base-commit expansion fails, and assert that warning in tests.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
libs/phabricator-client/phabricator_client/client.py	Adds fallback logic to expand abbreviated commits via unique prefix match in data when identifierMap is missing.
libs/phabricator-client/tests/test_client.py	Adds tests for mirrored repos, filtering non-expansion identifiers, and ambiguity handling.
agents/bug-fix/hackbot_agents/bug_fix/broker.py	Logs a warning when base commit cannot be expanded and falls back to the raw base.
agents/bug-fix/tests/test_broker.py	Updates the patch-route fallback test to capture and assert the warning log.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.