juju upgrade-charm requires --switch for local charms

[Casey Marshall]

Latest master (5f385be). Steps to reproduce:

1. Deploy a local charm (you can get gogs with `charm pull cs:~cmars/gogs` if you like):

$ juju deploy ~/trusty/gogs

2. Try to upgrade it

$ juju upgrade-charm gogs --force-units
ERROR unknown schema for charm URL "local:trusty/gogs"

You can workaround by using --switch, but this probably isn't the intended UX:

$ juju upgrade-charm gogs --force-units --switch ~/trusty/gogs
Added charm "local:trusty/gogs-1" to the model.

[Casey Marshall (cmars)]

I don't know if you need to change the local charm contents or not to get upgrade-charm to realize that it has work to do... If you do, a `make clean all` in gogs will do the trick.

[Ian Booth (wallyworld)]

Ah, this looks like fallout from removing local repo support.

[Ian Booth (wallyworld)]

When you upgrade a local charm, you must (re)supply the path to the charm.

$ juju upgrade-charm gogs --force-units

^^^^^ requires a path. So the cmd should flag that and abort the upgrade.

[Casey Marshall (cmars)]

Ah, that makes sense, it's certainly a side-effect of getting rid of local repos. As long as we make it clear to the user what to do in the error message, I think it's fine. As a new charmer I probably would have been stuck if I hadn't known about --switch and how it works.

[feng xia (fengxia41103)]

I'm not seeing document on `--switch`. Could someone pls point me to its introduction?