Function apply_flags 

pub fn apply_flags(
    dir: &Path,
    all: &[Loaded],
    flags: &[(String, String)],
    by: &str,
) -> Result<(), String>

Trusts the extensions flags name, each only at its current digest (via = ci).

Errors

A flag names no extension, one that cannot be loaded, or a digest that is not the current one (the message names it).