PreToolUse hook for the Bash tool. When the user writes a pipeline whose
left side changes state (git push, kubectl apply, curl -X PUT, ...) and
whose exit status is then consumed by && / || / an if-condition, the
hook exits 2 and surfaces an advisory naming the masking command and
suggesting ${PIPESTATUS[0]} or dropping the pipe.
Always exits 0 on parse failure, missing python3, empty input, malformed
JSON, or anything it does not recognise — a hook that breaks Bash is
worse than the bug it prevents.
Real-process tests in hooks/tests/ feed JSON on stdin as a subprocess and
include mutation cases (six targeted matcher breakages) to prove each
assertion can actually fail.
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