feat: add no-useless-cat rule

[nzakas]

Adds shell/no-useless-cat, which mirrors ShellCheck SC2002: cat file | cmd can be cmd < file or cmd file.

Behavior

• Reports a pipeline whose first command is cat with exactly one static, non-flag argument and no redirects.
• Not reported:
  • cat with several files (a real concatenation).
  • cat with flags (cat -n file | head).
  • Dynamic arguments such as cat "$f" | sort.
  • cat that isn't first in a pipeline.
• No autofix: whether cmd < file or cmd file is right depends on the command.
• Recommended config: "error".

Documentation

Adds docs/rules/no-useless-cat.md, following the format of the @eslint/json, @eslint/css, and @eslint/markdown rule docs: description, background, rule details with incorrect and correct examples, options, when not to use it, and the ShellCheck reference. The rule's meta.docs.url points at that file, and its README table entry links to it.

Testing

8 RuleTester cases and 5 documentation checks (279 total); build, lint, and format checks pass.

🤖 Generated with Claude Code

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📥 Commits

Reviewing files that changed from the base of the PR and between a7458b2 and f62c9b8.

📒 Files selected for processing (6)

• README.md
• docs/rules/no-useless-cat.md
• src/index.spec.ts
• src/index.ts
• src/rules/no-useless-cat.spec.ts
• src/rules/no-useless-cat.ts

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[Copilot]

Copilot review overview

🟡 Changes recommended

Shell expansion handling currently causes false positives for multi-file expansions and ANSI-C-quoted options.

Review effort: Balanced
Findings: 1

Open (1)

• Reject glob and brace expansions as single static filenames · New

What changed in this PR

Adds the recommended bash/no-useless-cat rule, modeled after ShellCheck SC2002.

Changes:

• Implements and registers the rule.
• Adds rule and plugin tests.
• Adds documentation and README metadata.

File	Description
src/​rules/​no-useless-cat.ts	Implements pipeline detection.
src/​rules/​no-useless-cat.spec.ts	Adds RuleTester cases.
src/​index.ts	Registers and recommends the rule.
src/​index.spec.ts	Verifies rule exposure.
README.md	Adds the rules-table entry.
docs/​rules/​no-useless-cat.md	Documents behavior and examples.

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[nzakas]

@copilot address review comments. Be sure to add tests.

[Copilot]

@copilot address review comments. Be sure to add tests.

Added checks for unquoted glob/brace patterns and ANSI-C-quoted arguments, with regression tests. Committed as 9312963.