In YAML, block scalars (`|` and `>`) silently add a trailing newline by default
("clip" chomping). This can cause subtle bugs when the newline is unintentional.
This PR adds a warning when clip chomping is used in fields where trailing
newlines commonly cause issues:
- Environment variables (workflow, job, step, container, service levels)
- Action inputs (`with:`)
- Reusable workflow inputs and secrets
- Job outputs
- Matrix values (including `include` and `exclude`)
- Concurrency groups
The warning suggests using `|-` (strip) or `|+` (keep) to be explicit.
Intentionally does NOT warn for:
- `run:` scripts (trailing newlines are normal)
- Fields trimmed server-side (`if:`, `name:`, `runs-on:`, etc.)
The feature is gated behind the `blockScalarChompingWarning` feature flag.
eric sciple
2816233a40