Function resolve_api_version 

pub fn resolve_api_version(
    long_flag: &str,
    env_var: &str,
    default: &str,
) -> String

Resolve a per-service API version selector by scanning the real process arguments directly. This has to happen before clap builds the Command tree (inside Args::augment_args), i.e. before any ArgMatches exist — so it can’t go through clap itself. Once the tree is built, the actual (clap-parsed, env-aware, default-applying) value is read normally from ArgMatches in FromArgMatches::from_arg_matches; this function is only ever used to decide which version’s subcommand tree to attach.