Fix clang-tidy-check: distinguish tooling failures from issue detection

[Copilot]

cmake --build . --target clang-tidy-check exits non-zero both when clang-tidy finds code issues and when a tooling failure occurs. The previous || true masked both cases, silently passing on real infrastructure failures.

Changes

• clang-tidy-check.yaml: Replace || true with explicit exit-code capture and log content analysis to distinguish the two non-zero cases:

Situation	Exit code	Log diagnostics	Outcome
clang-tidy found issues	non-zero	present	continue, report issues
tooling failure	non-zero	absent	::error:: + fail job
clean code	0	absent	report pass

cmake --build . --target clang-tidy-check -- --export-fixes clang-tidy-fixes.yaml > clang-tidy.log 2>&1
cmake_status=$?

# Distinguish tooling failures from issue detection by checking log content
if [ "$cmake_status" -ne 0 ]; then
  if ! grep -qE '^/.+\.(cpp|hpp|c|h):[0-9]+:[0-9]+: (warning|error):' clang-tidy.log; then
    echo "::error::clang-tidy failed without producing diagnostic output (exit code $cmake_status)"
    exit "$cmake_status"
  fi
fi

The heuristic checks for clang-tidy diagnostic output (file:line:col format) rather than relying on the fixes file, which is only populated when auto-fixes are available. Many clang-tidy checks do not provide automatic fixes.

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[greenc-FNAL]

@phlexbot format

[github-actions]

No automatic cmake-format fixes were necessary.

[github-actions]

No automatic markdownlint fixes were necessary.

[github-actions]

No automatic jsonnetfmt fixes were necessary.

[github-actions]

No automatic clang-format fixes were necessary.

[Copilot]

Pull request overview

This PR updates the clang-tidy GitHub Actions workflow to correctly differentiate “clang-tidy found issues” from “clang-tidy infrastructure/tooling failed,” so real tooling failures no longer get silently masked.

Changes:

• Capture the cmake --build ... clang-tidy-check exit code and analyze the log to decide whether to fail the job (tooling failure) or continue (issues found).
• Switch issue detection from “non-empty fixes YAML” to “diagnostic output present in log.”