Function parse_status_region 

pub fn parse_status_region(
    region: &[OsString],
    wrapper_flags: &[&[u8]],
) -> Result<StatusRegion, OptionError>

What: Parse the region after status. Result<A, B> is “either success A or failure B”. Why: A region Git itself would refuse yields the refusal, never a guessed fact.

In TS you’d write (pseudocode):

function parseStatusPostRegion(region: string[]): StatusPostRegion; // throws