Function resolve_pull_invocation 

pub fn resolve_pull_invocation(
    config: &ConfigSet,
    remote: Option<&str>,
    refspecs: &[String],
    current_branch: Option<&str>,
) -> FetchInvocation

Classify grit pull [<remote>] [<refspec>…] positionals.

Same rules as resolve_fetch_invocation, but the default remote comes from configured_remote_for_pull, so a branch tracking a local branch yields ..