clare: Instructions file for GitHub Copilot

Script Authoring Rules (CLARE — Constrained)

All scripts in scripts/ follow these rules. Violations cause verify-ci.sh to fail.

Required

• Shebang: #!/usr/bin/env bash (not /bin/bash)
• Safety flags: set -euo pipefail at the top of every script
• Self-documenting header: Block comment describing purpose, usage, and options
• Executable: Scripts must be chmod +x

Quoting and Variables

• Always quote variables: "$var" not $var
• Use [[ ]] for conditionals, not [ ]
• Use $() for command substitution, not backticks
• Use readonly or local to scope variables appropriately

Error Handling

• Check return codes explicitly when set -e would mask the intent
• Use || true only when failure is genuinely acceptable and comment why
• Provide human-readable error messages before exiting

Output

• Use color codes for status (see verify-ci.sh helper pattern)
• Use >&2 to write errors to stderr
• Keep stdout machine-parseable when scripts are used in pipelines

Portability

• Target bash 4.0+ (available on all modern Linux/macOS with Homebrew)
• Do not assume GNU-specific flags for sed, awk, date without checking
• Use command -v tool to test for tool availability before use

Prohibited

• rm -rf without explicit user confirmation or --force flag
• Hardcoded credentials or tokens
• curl | bash patterns
• Suppressing errors with 2>/dev/null unless explicitly justified in a comment