message: Fix HgRepo::discover
  Replace the duplicate .cwd call with an invocation taken from
  Match the semantics of the other vcs calls, which is invoke from 'cwd'
  targeting 'path'. Looks a little confusing because hg takes a '--cwd'
  argument.
diff: @@ -28,8 +28,9 @@ impl HgRepo {
  pub fn discover(path: &Path, cwd: &Path) -> CargoResult<HgRepo> {
  process("hg")
  .cwd(cwd)
  + .arg("--cwd")
  + .arg(path)
  .arg("root")
  - .cwd(path)
  .exec_with_output()?;
  Ok(HgRepo)
  }
  