pub fn reject_flag_like(program: &str, what: &str, value: &str) -> Result<()>Expand description
Injection guard for bare positional argv slots: a caller-supplied value with a
leading - would be parsed by the CLI as a flag (verified: git checkout -evil → “unknown switch”; jj likewise), and an empty (or whitespace-only)
value silently changes most commands’ meaning. Refuse both before anything
spawns, surfacing an Error::Spawn naming program. Flag-VALUE positions
(-m <msg>, --branch <b>) don’t need this — the CLI consumes the next
token verbatim there.