add recommended workflow for copier updates

[gilesknap]

For projects that have not been updated for a long time I found the documented workflow helped avoid confusion of changing the template and tool versions simultaneously.

[GDYendell]

Did just updating dependencies and fixing before doing the update make it easier in some case? I always just update and fix everything in one go.

[gilesknap]

Did just updating dependencies and fixing before doing the update make it easier in some case? I always just update and fix everything in one go.

So my assertion is that if there is a long break between updates. Having both new ruff (or other) errors to contend with and the changes themselves was too much.

I guess this came about because I was updating to latest from an early beta version of copier template.

When the checks don't even run because of fundamental issues (in my case a missing _version.py) then it's difficult to know where the problem is coming from.

Perhaps I'm over thinking this though. I guess fixes for both causes of error can be performed together. My particular scenario was extreme.

I'm reasonably happy to close without merging.

[GDYendell]

Squash and merge?

[coretl]

I disabled it for the repo as we sometimes adopt from a branch and squashing loses the update ability. This doesn't apply here, so will re-enable it just for this PR...