Function split_shell_spec 

pub fn split_shell_spec(spec: &str) -> Option<Vec<String>>

Splits a [general] shell spec into the argv prefix it stands for.

The spec is a program name followed by the flags that make that program read a command string, for example pwsh -NoProfile -Command. Tokens are separated by whitespace; a double-quoted run is one token, which is how a program path containing spaces is written. Backslashes are literal, so a Windows path needs no doubling here — though TOML itself still requires a literal string ('...') or doubled backslashes to deliver one.

Returns None when the spec cannot be used as an argv prefix: it is blank, it leaves a quote unterminated, or its first token — the program to spawn — is empty. shell_argv reads None as “fall back to DEFAULT_SHELL_ARGV”, and TrailConfig::validate rejects a non-blank spec that returns None so the user hears about a typo at startup.

use trail::actions::shell_exec::split_shell_spec;

assert_eq!(
    split_shell_spec("pwsh -NoProfile -Command"),
    Some(vec!["pwsh".to_owned(), "-NoProfile".to_owned(), "-Command".to_owned()])
);
assert_eq!(
    split_shell_spec("\"C:/Program Files/PowerShell/7/pwsh.exe\" -Command"),
    Some(vec![
        "C:/Program Files/PowerShell/7/pwsh.exe".to_owned(),
        "-Command".to_owned(),
    ])
);
assert_eq!(split_shell_spec("   "), None);
assert_eq!(split_shell_spec("\"unterminated -c"), None);