Add tox env for noble

[sed-i]

Issue

We need to release a noble (24.04) revision, which only charmcraft v3 can do: with charmcraft 2.x, we'd get for noble:

No suitable 'build-on' environment found in 'bases[0]' configuration.

With charmcraft 3, if we try to add it to the existing list of build-on, charmcraft errors out with:

Bad charmcraft.yaml content:
- base requires 'platforms' definition: {'name': 'ubuntu', 'channel': '24.04', 'architectures': ['arm64']} (in field 'bases[0]')

because charmcraft v3 won't pack noble when charmcraft.yaml has the old schema.

Solution

• Use charmcraft 3 for all builds, but have two different charmcraft.yaml files:
  • charmcraft-22.04.yaml, which is identical to before;
  • charmcraft-24.04.yaml, with the new base schema.
• Also keep charmcraft.yaml so existing github CI still works as before.
• Keep releasing noble manually until a better solution emerges.

Fixes #155.

Drive-by fixes:

• Consolidate metadata, config into charmcraft.yaml.

Context

Testing Instructions

Upgrade Notes

[ca-scribner]

What about making these do:

• backup current charmcraft.yaml
• make their own charmcraft.yaml pointing to the right thing
• pack
• restore charmcraft.yaml
  ?

It feels odd that 22.04 and 24.04 have different properties around their statefulness. Agreed that it'll work atm, but this is an easy thing for someone to misuse without realizing.

[sed-i]

Not sure what's the benefit of this approach.

• If we symlink then if someone interrupts the 24.04 and git add . then we'd see a small diff (the symlink changed from 22.04 to 24.04).
• If we use a third copy of the yaml + untracked backup, then if someone git add . then we'd see a slightly larger diff (the charmcraft.yaml will have an entire section replaced).

A symlink seems cleaner. What am I missing?

[ca-scribner]

I'm not against a symlink, just the asymmetry between the two versions:

• 22.04 changes the charmcraft.yaml to the current case, packs
• 24.04 changes the charmcraft.yaml to the current case, packs, and then back to a different case

They don't feel equivalent enough to bundle together. They'll work atm, but someone in future is going to miss that subtlety. What I'm proposing is:

• X: backs up charmcraft.yaml, changes charmcraft.yaml to X, packs, restores backed up charmcraft.yaml

That way all versions of the environment work the same.

[ca-scribner]

An alternative would be have only a pack-24.04 environment (no 22.04). That feels more suitable imo, since the idea is packing for 24.04 is currently a special, manual case.

[ca-scribner]

hah, I see @lucabello asked about this too. I like his original suggestion (or, doing the same thing but with backing up symlinks).

[sed-i]

Huh, yeah, might as well drop the 22.04 option. Thanks!

[ca-scribner]

lgtm, but I'd rework the tox env to either work the same for all bases or to just implement a single pack-24.04 env