conf: hierarchical configuration path

[oliver-sanders]

Cylc Flow has a configuration file hierarchy which allows us to provide different configuration for different installed versions of Cylc E.G:

• ~/.cylc/flow/global.cylc
• ~/.cylc/flow/8/global.cylc
  *~/.cylc/flow/8.0/global.cylc

The UIS/Hub could probably do with the same treatment.

I would make more sense to use the Cylc Flow (meta) version for this hierarchy because:

• It is already used for this purpose.
• The UI Server version isn't user-facing (visible via cylc version --long).
• The Hub version is obscure (implementation detail visible via pip list).

Pull requests welcome!

[MetRonnie]

Is this not already implemented? E.g. see #252

[oliver-sanders]

No, this issue is about adding the version number to the configuration hierarchy.

[oliver-sanders]

Should be easy, can copy the solution from cylc-flow. This will protect sites from future interface changes.

[oliver-sanders]

Update: The meta package is no more.

Meeting: Change the config dir from hub to uiserver (#291) and add the uiserver to the hierarchy.

~/.cylc/uiserver/<uiserver-version>