state: rename Unit.Name to Unit.Id

state: rename Unit.Name to Unit.Id

This is a preparatory step to renaming PathKey to Name.

Also changed a couple of tests to use PathKey rather than Id.

https://code.launchpad.net/~rogpeppe/juju-core/097-state-unit-id/+merge/127341

(do not edit description out of merge proposal)

[rog, 2012-10-01 17:57:25]

Please take a look.

[niemeyer, 2012-10-01 18:23:28]

I've reviewed about 80% of this with trivial comments only, and then when I got
to reviewing the service bits, I got deadlocked.

You wisely decided not to switch service.Name to mean "service-wordpress",
because that'd mean the service name, which is a sane concept, wouldn't be a
service name. That, in turn, means the unit Name means something totally unlike
the service Name, so we get unit.Name() => "unit-wordpress-0", but
service.Name() => "wordpress".

Also, there are public parts of the interface, such as the JUJU_UNIT_NAME
environment variable, that we can't change, so we're introducing gratuitous
inconsistencies that we can't avoid with our renaming.

I suggest dropping our idea of replacing what the Name methods mean, and instead
doing a simpler change that introduces a Key method that returns the equivalent
of PathKey today, and dropping PathKey:

machine.Key() => "machine-0"
unit.Key() => "unit-wordpress-0"
service.Key() => "service-wordpress"

We can also have PrincipalKey in state.Info.