auto:percent becomes the default format for exporting as script

[mwouts]

Will close #1160

[github-actions]

Thank you for making this pull request.

Did you know? You can try it on Binder: or .

Also, the version of Jupytext developed in this PR can be installed with pip:

pip install git+https://github.com/mwouts/jupytext.git@percent_format_is_the_default_for_saving_scripts

(this requires nodejs, see more at Developing Jupytext)

[mahendrapaipuri]

@mwouts Let me know if you need a hand on extension part. I think we did not include about linting the extension manually before push in the docs. Unfortuantely we could not integrate linting the extension in pre-commit due to the repo layout. You will need to run jlpm lint:check for dry-run and jlpm lint to actually lint the extension from jupyterlab directory.