message: Fix bash completion on mac.
  For some bizarro reason, mac's bash doesn't like negative indexes,
  even though its version of bash should support it.
diff: @@ -125,7 +125,7 @@ __cargo_commands=$(cargo --list 2>/dev/null | tail -n +2)
  _locate_manifest(){
  local manifest=`cargo locate-project 2>/dev/null`
  # regexp-replace manifest '\{"root":"|"\}' ''
  - echo ${manifest:9:-2}
  + echo ${manifest:9:${#manifest}-11}
  }
  # Extracts the values of "name" from the array given in $1 and shows them as
  