Never output table borders. It’s noisy and a huge pain for parsing using other
tools such as `grep`.

Be mindful of the screen width. Only show a few columns by default with the
table header, for more the table can be manipulated by the following options:

- `--no-headers`: Show column headers by default but allow to hide them.
- `--columns`: Comma-separated list of column names to add.
- `--sort`: Allow sorting by column. Allow inverse and multi-column sort as well.

## Interactive output

Interactive output was selected to be able to strike the balance between
beginners and advance users. While the default output will target beginners it
can, with a few key strokes, be changed into and advance introspection tool.

### Progress

For longer running commands we should provide and overview the progress.
This is shown best in `nix build` example:

```shell
$ nix build
    Started building my-project 1.2.3
 Downloaded python3.8-poetry 1.2.3 in 5.3 seconds
 Downloaded python3.8-requests 1.2.3 in 5.3 seconds
------------------------------------------------------------------------
      Press `v` to increase logs verbosity
         |> `?` to see other options
------------------------------------------------------------------------
      Learn something new with every build...
         |> See last logs of a build with `nix log --last` command.
------------------------------------------------------------------------
  Evaluated my-project 1.2.3 in 14.43 seconds
Downloading [12 / 200]
         |> firefox 1.2.3 [#########>       ] 10Mb/s | 2min left
   Building [2 / 20]
         |> glibc 1.2.3 -> buildPhase: <last log line>
------------------------------------------------------------------------
```

### Search

Use a `fzf` like fuzzy search when there are multiple options to choose from.

```shell
$ nix init
Initializing Nix project at `/path/to/here`.
      Select a template for you new project:
          |> py
             template#python-pip
             template#python-poetry
             [ Showing 2 templates from 1345 templates ]
```

### Prompt

In some situations we need to prompt the user and inform the user about what is
going to happen.

```shell
$ nix build --option substitutors https://cache.example.org
------------------------------------------------------------------------
  Warning! A security related question needs to be answered.
------------------------------------------------------------------------
  The following substitutors will be used to in `my-project`:
    - https://cache.example.org

  Do you allow `my-project` to use above mentioned substitutors?
    [y/N] |> y
```

## Verbosity

There are many ways that you can control verbosity.

Verbosity levels are:

- `ERROR` (level 0)
- `WARN` (level 1)
- `NOTICE` (level 2)
- `INFO` (level 3)
- `TALKATIVE` (level 4)
- `CHATTY` (level 5)
- `DEBUG` (level 6)
- `VOMIT` (level 7)

The default level that the command starts is `ERROR`. The simplest way to
increase the verbosity by stacking `-v` option (eg: `-vvv == level 3 == INFO`).
There are also two shortcuts, `--debug` to run in `DEBUG` verbosity level and
`--quiet` to run in `ERROR` verbosity level.

----------

# Appendix 1: Commands naming exceptions

`nix init` and `nix repl` are well established