rust/rhg/src/exitcode.rs

rhg: add RootCommand using hg-core FindRoot operation to prepare `hg root`

The println macro is not used to avoid string usage.
Dealing only with bytes allows us to be compatible with any encoding
and not just UTF8.

Later on, format macro will be made to have more readable code.

Differential Revision: https://phab.mercurial-scm.org/D8612

pub type ExitCode = i32;

/// Successful exit
pub const OK: ExitCode = 0;

/// Generic abort
pub const ABORT: ExitCode = 255;

/// Command not implemented by rhg
pub const UNIMPLEMENTED_COMMAND: ExitCode = 252;