Add COSIMA metadata to attributes of data returned from getvar

[aidanheerdegen]

The cookbook has access to metadata with important provenance information. It makes sense to add this metadata to the xarray.DataArray returned by getvar.

Could add a flag to toggle this behaviour (default to adding the metadata), but I'm leaning away from that. It adds complexity to the API and it isn't hard to ignore/delete attributes that aren't required. Including it will only ever be useful for researchers, even if they only realise it a year later when they have some data and can't recall the details of where it came from, but that information is available in the global attributes.

[aidanheerdegen]

Any issues with this @AndyHoggANU, @aekiss or @navidcy?

I think this, in addition to #262 will help a lot with provenance and allow end users to understand better where their data came from and how it was constructed.

[AndyHoggANU]

I don't think I would have any issues -- as long is it doesn't slow down variable retrieval? Provenance always good.

[aidanheerdegen]

Won't make any difference to variable retrieval but I'll check.

[navidcy]

The cookbook has access to metadata with important provenance information. It makes sense to add this metadata to the xarray.DataArray returned by getvar.

This makes absolute sense, of course. I don't understand why it's something worth debating for..

[aidanheerdegen]

You never know what people might object to. Also prioritising work can help to know if something is considered worthwhile.

[navidcy]

The only concern would be performance, as @AndyHoggANU pointed out.

[navidcy]

But even a slight performance loss is still worth it... Loading variables never takes that long anyways... (imo)