ci(bazel): restore change-aware matrix scheduling

[balajinvda]

Why

Since #343 merged, every PR rebuilds and tests every service, including docs-only changes like #423. #343 (commit f286e51) added a blanket run_all=true override on top of the change-aware scheduler that had been working since commit 126c56b (feat(ci): change-aware GHA bazel matrix). The override was a safety net while debugging cloud-tasks test output during that import, and is no longer needed.

Each subtree is an isolated Bazel module, so a change under one service builds and tests only that service's //... and cannot break another module. Forcing the full matrix on unrelated changes just burns queue time (and pays a cold rebuild on the bazel-docker lanes, which only warm on main pushes).

What changed

Remove the unconditional run_all=true override in the detect job, restoring change-aware scheduling. Everything else is intentionally unchanged:

• Reverse-dependency edges: a Java framework change (nv-boot-parent) still fans out to every Java service (cloud-tasks); shared Java/root infra still schedules every Java row; ROOT_GLOBS still select the root row.
• Full-matrix fallbacks stay: workflow_dispatch, a change to this workflow itself, and unreadable/rewritten/new-branch diffs.
• A docs-only or helm-only change selects zero rows; the bazel-verification gate passes on any=false.

Customer Release Notes

Not customer visible (CI-only).

Testing

Traced the detect selection logic against representative changesets:

• grpc-proxy source change -> only the grpc-proxy row.
• nv-boot-parent change -> nv-boot-parent plus every java-service (cloud-tasks) rebuilt and tested in its docker-host lane.
• docs-only change (as in docs: update 0.6.1 release candidate manifest #423) -> zero rows; verification gate exits 0 on any=false.

YAML validated with a parser; the unconditional run_all=true assignment is removed while the conditional fallbacks remain.

References

Override introduced in #343 (f286e51). Change-aware scheduling originally landed in 126c56b.

Summary by CodeRabbit

• Bug Fixes
  • Bazel build and test workflows now run only the affected modules and their dependent Java targets by default.
  • Full workflow coverage remains available for manual runs, workflow changes, and changes that cannot be safely analyzed.
  • Improved workflow guidance clarifies how root-level Java dependency or configuration changes are handled.

[coderabbitai]

📝 Walkthrough

Walkthrough

The Bazel workflow now uses existing change-aware detection to select affected subtree modules and Java reverse-dependency rows, while retaining full-matrix fallbacks for dispatches, workflow changes, and unsafe or unknown diffs.

Changes

Bazel workflow scheduling

Layer / File(s)	Summary
Enable change-aware matrix detection .github/workflows/bazel.yml	Removes the unconditional run_all=true override and documents subtree selection, reverse-dependency edges, no-op paths, full-matrix fallbacks, and root-owned Java dependency handling.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: apartha-nv

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title follows Conventional Commits and accurately describes this CI-only Bazel workflow scheduling change.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/change-aware-bazel-matrix

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In @.github/workflows/bazel.yml:
- Around line 174-184: Replace every pipelined printf-to-grep path match in the
change-aware scheduling logic with a non-pipelined check against the
changed-path data, such as a here-string passed to grep with fixed-string
matching. Update the workflow, framework, and subtree tests while preserving
their existing match semantics and scheduling behavior.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: d5529ef2-db6e-41da-88ec-4aa3ec799354

📥 Commits

Reviewing files that changed from the base of the PR and between 2961f91 and 2a391c8.

📒 Files selected for processing (1)

• .github/workflows/bazel.yml