rhg: Do not return error when when we really mean ok in commands

Before when a command was successfull `Err(CommandErrorKind::Ok.into())` was
returned which is an oxymoron. Using `Ok(())` when everything is ok seems more
appropriate.

Differential Revision: https://phab.mercurial-scm.org/D8864

rust/rhg/src/commands/root.rs

@@ -29,7 +29,7 b' impl RootCommand {'
         // TODO use formating macro
         self.ui.write_stdout(&[bytes.as_slice(), b"\n"].concat())?;
 
-        Err(CommandErrorKind::Ok.into())
+        Ok(())
     }
 
     fn display_error(&self, error: FindRootError) -> Result<(), CommandError> {

rust/rhg/src/error.rs

@@ -5,8 +5,6 b' use std::convert::From;'
 /// The kind of command error
 #[derive(Debug, PartialEq)]
 pub enum CommandErrorKind {
-    /// The command finished without error
-    Ok,
     /// The root of the repository cannot be found
     RootNotFound,
     /// The current directory cannot be found
@@ -20,7 +18,6 b' pub enum CommandErrorKind {'
 impl CommandErrorKind {
     pub fn get_exit_code(&self) -> exitcode::ExitCode {
         match self {
-            CommandErrorKind::Ok => exitcode::OK,
             CommandErrorKind::RootNotFound => exitcode::ABORT,
             CommandErrorKind::CurrentDirNotFound => exitcode::ABORT,
             CommandErrorKind::StdoutError => exitcode::ABORT,