`juju switch -` doesn't switch to previous model

[Jack Shaw]

More of a feature request

Lots of cli tools with a navigation aspect use the dash character to navigate back to the previous place. Such as `cd` and `git checkout`

I think it would be great if `juju switch` could do a similar thing!

setup:
```
$ juju models
Controller: lxd

Model Cloud/Region Type Status Machines Units Access Last connection
controller localhost/localhost lxd available 1 1 admin just now
default* localhost/localhost lxd available 3 3 admin 42 seconds ago

$ juju switch controller
lxd:admin/default -> lxd:admin/controller
```

expected (requested) behaviour
```
$ juju switch -
lxd:admin/controller -> lxd:admin/default
```

actual behaviour
```
juju switch -
ERROR model name "admin/-" not valid
```

[Vitaly Antonenko (anvial)]

Thx Jack,

Sounds reasonable.

[Jordan Barrett (barrettj12)]

https://juju.is/docs/olm/juju-stash is related, originally written by Simon IIRC. I'm not sure if it's been tested recently / works with newer versions of Juju.

[Guillaume Fouillet (gfouillet)]

This may be tricky in case of multiple controller, because juju switch can either switch over controller or model, with disambiguation done on the given arg

* juju switch mymodel => switch model
* juju switch mycontroller => switch controller

However, there is already a way of disambiguation through semicolon

* juju switch :- => could switch model
* juju switch -: => could switch controller

Some question may requires decision, like above behavior:

* juju switch - => switch what ? (by default, it is the controller which is prioritized, so `git switch something` will switch to something controller if both something model and controller exists in context)
* juju switch -:mymodel => Is it ok ? What does it do ?
* juju switch mycontroller:- => Is it ok ? What does it do ?

A proper and consistent behavior for this feature would be:

- juju switch :- => switch model
* juju switch -: => switch controller
* juju switch - => By default, switch controller. However, if there is only one controller registered into the client, switch model (this ambiguous command shouldn't be used in CI script, obviously)

[Guillaume Fouillet (gfouillet)]

https://github.com/juju/juju/pull/17516

[Simon Richardson (simonrichardson)]

This should be in 4.0, I'd like to bake this in before sending it on 3.6. If we do like this, we can always back port it.