This PR improves the rendering of card panes, but note that this change still doesn't bring the concerned page in visual agreement with what the paged looked like before.

Before (https://deploy-preview-1356--docsydocs.netlify.app/docs/adding-content/shortcodes/#card-panes):

With this PR (https://deploy-preview-1376--docsydocs.netlify.app/docs/adding-content/shortcodes/#card-panes):

Could you add an entry to the CHANGELOG, under breaking-changes so that users are aware of the class name change?

Done.

This PR improves the rendering of card panes, but note that this change still doesn't bring the concerned page in visual agreement with what the paged looked like before.

I was aware of this when submitting the PR.

From the bootstrap migration guide

BREAKING: Dropped .card-deck in favor of our grid.
Wrap your cards in column classes and add a parent .row-cols-* container
to recreate card decks (but with more control over responsive alignment).

Using of the bootstrap grid in the cardpane shortcode would mean a major rework of the shortcode. I fiddled around with adding a margin/padding to the individual cards, with no satisfactory results. Yes, the page looks different, but it doesn't look bad IMHO. I would leave this as is for now.

This PR improves the rendering of card panes, but note that this change still doesn't bring the concerned page in visual agreement with what the paged looked like before.

On a second attempt, I now was able to bring the concerned page in visual agreement with what the page looked before.
The PR now also closes #1158.

Also pls rebase,

Done.

then I'll do a final review.

Thanks.

Following up on #906, I reworked the card shortcode by adding a second commit to this PR. This commit introduces the following changes:

• shortcode card, card-code: markup of inner content (html/markdown) now depends on the syntax of the calling shortcode, not on extension of page file any more.
• deprecated shortcode card-code, you can now use shortcode card with named parameter code=true instead.
• Simplified and improved code of shortcodes.

Is layouts/shortcodes/card-code.html actually still used?

No, in the userguide, we don't use it any more.

It seems to me that this PR was getting rid of it, but the file is still present.

CHANGELOG:

- shortcode `card-code` is now deprecated, use shortcode `card` with named
    parameter `code=true` instead.

I wrote deprecated, which means the file is still present and works, but it is not documented any more and users are discouraged to further use this shortcode.

but the file is still present.

Yes, this is intentional: if I remove the shortcode, this will break all existing pages that make use of this shortcode and we will force users to adapt their pages (by replacing shortcode card-code with card).

Does that clarify things? Would you like to see the file deleted?

Other than the question about card-code and border, LGTM. Thanks!

I rebased the PR to get it ready for merging. Let me know if you want me to delete the card-code shortcode. Styling issues will be addressed in a separate issue, to be opened shortly. Thanks for your thorough review, I appreciate your comments.