pre-commit config

[zmoon]

Based on xgcm's config but adding pyupgrade and facilitating the current longer line-length setting.

[zmoon]

@jbusecke I wanted to see what you thought of this config before I apply it. Also wait for #73 to be merged I suppose.

[codecov]

Codecov Report

Merging #90 (60ae494) into master (7886817) will decrease coverage by 0.13%.
The diff coverage is 95.83%.

@@            Coverage Diff             @@
##           master      #90      +/-   ##
==========================================
- Coverage   78.65%   78.52%   -0.14%     
==========================================
  Files           3        3              
  Lines         328      326       -2     
  Branches       61       61              
==========================================
- Hits          258      256       -2     
  Misses         46       46              
  Partials       24       24              

Flag	Coverage Δ
unittests	78.22% <95.83%> (-0.14%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
setup.py	0.00% <ø> (ø)
xmovie/core.py	85.12% <94.11%> (-0.16%)	⬇️
xmovie/presets.py	69.76% <100.00%> (ø)

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[jbusecke]

Hey @zmoon for this to work in the 'old way' you would have had to add a github workflow file, but I have started switching repos over to the pre-commit service. This is convenient since it does make linting corrections automatically!
Should we add this as part of this PR? If you agree, I would suggest to keep the line length as is (the bot should fix the code!), and I can activate the service.

[jbusecke]

I just activated the service just in case. We should also add

[![pre-commit.ci status](https://results.pre-commit.ci/badge/github/jbusecke/xmovie/master.svg)](https://results.pre-commit.ci/latest/github/jbusecke/xmovie/master)

to the README (I just tried to make a PR on your PR, but it didnt work for some reason).

[jbusecke]

I also think we can put this PR in front of #73, which might need some more iterations.

[zmoon]

the pre-commit service

Great, pre-commit ci is very nice. We should still do a pre-commit run --all-files here or later though.

tried to make a PR on your PR

You should be able to checkout my PR and commit. I can do it though.

[zmoon]

I'm going to start resolving the failed checks here.