This makes `git list` a lot faster (10 minutes to under 2 minutes in one
test) and displays more useful information.
Example of `git list` from before this change demonstrating that `git
list` was hiding the information about the main repository in favour of
showing information about a `composer` dependency:
```
├── iguana-extras
│ └── vendor
│ └── dxw
│ └── iguana HEAD ok
│ master ok
```
Example from after this change:
```
├── iguana-extras master [ 1 untracked ]
│ feature/readme no upstream
│ feature/update-iguana no upstream
│ fix/php-cs-fixer no upstream
```
