Forward help/version flags to tasks in run alias

[kjanat]

Summary

The run alias now intelligently forwards --help/-h and --version/-V flags to tasks when they follow a task name, while still printing the binary's own help/version when these flags appear before any task. This eliminates the need for the run <task> -- workaround to pass help flags to tasks.

Key Changes

• Disabled clap's built-in help/version flags on RunAliasCli to prevent them from short-circuiting parsing. This allows the flags to be treated as undefined hyphen tokens that can be forwarded to tasks via the trailing_var_arg mechanism.

• Added builtin request classification via new alias_builtin_request() function that detects when a parse error represents a help/version request (identified by UnknownArgument errors for these flags before any task).

• Added print_run_alias_help() function to render the binary's own help when -h/--help precedes any task, using argv[0] for the bin name to match previous behavior.

• Updated error handling in run_alias_in_dir() to intercept parse errors and classify them as builtin requests, routing them to appropriate handlers (help/version output) instead of rendering clap errors.

• Updated help text to document the new forwarding behavior and clarify when flags are interpreted as the binary's own vs. forwarded to tasks.

Implementation Details

The solution leverages clap's argument parsing mechanics:

• A leading --help/--version (before any task) cannot fill the hyphen-rejecting task positional argument, so it surfaces as an UnknownArgument error that we recognize and handle.
• A trailing --help/--version (after a task) is captured by args with trailing_var_arg = true and allow_hyphen_values = true, allowing it to be forwarded to the task.
• The -- separator continues to work for forcing literal forwarding of these flags.

Comprehensive test coverage added for all scenarios: forwarding after tasks, interleaved flags, double-dash handling, and leading builtin detection.

[coderabbitai]

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