Make plot templates optional

This is for discussion.

Not all of us use plots when using dvc, so for many repositories when you do dvc init it will add a folder .dvc/plots with a lot of json files that end up being unused. It would be good to have an option to ignore these files, say

dvc init --no-plots

Then if the user don’t have it and tries to do anything with dvc plot we create these templates (or perhaps throw an error saying they have to initialise a template).

[pmrowla]

What about bundling the default templates in the dvc package directory (so including them in MANIFEST.in and package_data in setup.py) instead of populating .dvc/plots/ with the defaults?

So by default when .dvc/plots/<template_name>.html doesn’t exist we would look for it in pkg_resources.resource_filename('dvc.plots', 'templates/<template_name>.html').

If users want to override the defaults they can continue to do so in .dvc/plots/... (and we should provide some init command or flag to copy the current defaults into .dvc/plots for users to start with).

For users that are not using their own custom plots, they would just have an empty/nonexistent .dvc/plots/ dir and always get the latest default template (via whatever DVC release they are using) and users that are using their own customized versions would just continue to use their custom one instead of the latest default. (In the case for users customizing their own templates, they would be responsible for keeping them up to date with DVC releases as needed)

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If we do it this way we could also just allow users to specify their own plots directory entirely (and search for matching templates in [custom_dir, .dvc/plots, DVC_PKG_DIR/plots/templates] with some documented priority) so that they can more easily use some shared set of plot templates between projects as needed

[dberenbaum]

Right, I forgot about that idea! That should make it easy to show the templates in the repo, but let’s not add any of this to #6550. Let’s address in a separate PR.