The wordpress.com AMP version doesn't support Gist embeds

[mehigh]

We should check the final version would have support for Github GIst them, as they're text-only.

needs-testing

[westonruter]

See list of core embeds being targeted here: #806 (comment)

Support for oEmbeds Gists are added by Jetpack: https://github.com/Automattic/jetpack/blob/b4ee9f55cb3819ffb4ce519c668130282e1a3544/modules/shortcodes/gist.php#L9-L10

There is an amp-gist component which can be used here.

The best move here would probably to open a PR to Jetpack to add a new AMP_Base_Embed_Handler subclass for AMP_Gist_Embed_Handler which can do similarly to what can be seen in the Tweet embed support: https://github.com/Automattic/amp-wp/blob/develop/includes/embeds/class-amp-twitter-embed.php

[westonruter]

Closing as duplicate of #375.