BuildStream's Confusing Terminal Output

[See original issue on GitLab](https://gitlab.com/BuildStream/buildstream/-/issues/478)
In GitLab by [[Gitlab user @finnball]](https://gitlab.com/finnball) on Jul 18, 2018, 12:11

## Background

Used BuildStream to make a project and struggled to understand the Terminal output. I can make educated guesses but for new users, this isn't good enough. For example:

```
[--:--:--][d3afc705][fetch:freedesktop-sdk-junction.bst:base/autoconf.bst] START Fetching https://ftp.gnu.org/gnu/autoconf/autoconf-2.69.tar.xz
================================================================================= 00:00:31 doom (282/282) =================================================================================
(Tracked:0 0 0)→ (Fetched:16 135 0)→ (Built:4 0 0)
~~~~~ Active Tasks ~~~~~
[00:00:11][Build:bootstrap-junction.bst:dependencies/base-sdk-image.bst] [00:00:11][Fetch:bootstrap-junction.bst:gcc-stage1.bst ]
[00:00:11][Fetch:bootstrap-junction.bst:libstdc++-stage1.bst ] [00:00:11][Fetch:bootstrap-junction.bst:gcc-stage2.bst ]
[00:00:11][Fetch:bootstrap-junction.bst:attr.bst ] [00:00:11][Fetch:bootstrap-junction.bst:acl.bst ]
```

A lot of these numbers don't make sense to me. What are these numbers and their various lanes doing?

```(Tracked:0 0 0)→ (Fetched:16 135 0)→ (Built:4 0 0) ```

This fraction rarely changes and I don't understand what it means

```doom (282/282)```

What's the difference between everything in the Active window and everything above?

## Ideas for solutions

* Write docs explaining the Terminal output
* Add more sensible labels

The issue names no files, tests, or entry points; begin with the linked GitLab report and reproduce the shown terminal output. Identify what the counters, progress line, and Active Tasks window mean, then document them or define clearer labels and a way to verify the result.

Written by the indexing model from the issue text.