path: extract sub-option logic into its own method
We will need to re-use this logic for `path://` so we first extract it into its own method.
Differential Revision: https://phab.mercurial-scm.org/D10262
pub type ExitCode = i32;
/// Successful exit
pub const OK: ExitCode = 0;
/// Generic abort
pub const ABORT: ExitCode = 255;
// Abort when there is a config related error
pub const CONFIG_ERROR_ABORT: ExitCode = 30;
/// Generic something completed but did not succeed
pub const UNSUCCESSFUL: ExitCode = 1;
/// Command or feature not implemented by rhg
pub const UNIMPLEMENTED: ExitCode = 252;