bisect-aware-instrumentation

# Bisect-Aware Instrumentation ## Overview Instrument code to support efficient git bisect operations by producing deterministic pass/fail signals and concise runtime summaries. This skill helps create robust test scripts that work reliably with `git bisect run`, handling edge cases like flaky tests, build failures, and non-deterministic behavior. ## Core Workflow ### 1. Understand the Regression Before instrumenting, clarify: - What behavior changed? (bug introduced, performance regression, test failure) - What is the "good" commit? (known working state) - What is the "bad" commit? (known broken state) - How to reproduce the issue? (test command, manual steps) ### 2. Create Bisect Test Script Generate a test script that returns proper exit codes for git bisect: **Exit Code Convention**: - `0`: Good commit (test passes) - `1-124, 126-127`: Bad commit (test fails) - `125`: Skip commit (cannot test - build failure, missing dependencies) **Template**: ```bash #!/bin/bash # bisect_test.sh - Test script for git bisect run set -e # Exit on error # Build/setup phase if ! make build 2>/dev/null; then echo "SKIP: Build failed" exit 125 fi # Run test with timeout timeout 30s ./run_test || TEST_RESULT=$? # Interpret results if [ $TEST_RESULT -eq 0 ]; then echo "GOOD: Test passed" exit 0 elif [ $TEST_RESULT -eq 124 ]; then echo "SKIP: Test timeout" exit 125 else echo "BAD: Test failed with code $TEST_RESULT" exit 1 fi ``` ### 3. Add Determin...