Move REST API Handbook content to GitHub

[rmccue]

Much like wp-cli, the REST API documentation would greatly benefit from being on GitHub, and using an open editing process.

I've adapted the existing code used to power the wp-cli commands reference on DevHub into a new generic plugin. The CLI code has been updated to use this, and new API code is added to move our handbook there too. Patch incoming momentarily.

Do not commit this yet. I want to maintain the syncing plugin on GitHub and either pull it in as an svn external instead, or sync it manually.

cc @danielbachhuber

[rmccue]

Add WPORG Markdown plugin for CLI/API handbooks

[rmccue]

2968.diff​ adds a new WPORG Markdown plugin that just provides the base class used by the CLI (commands) and REST API handbooks. It doesn't update the CLI Handbook proper to use it yet, since that has a bit more functionality, but it will. Will require the CLI Handbook's manifest to be updated though, since it's incompatible.

In the process of extracting this out, I added a few extra bits of functionality not in the existing classes:

• Updating existing pages - If an existing page is found, it will now update the source URL. This allows us to retrofit into existing Handbooks (like the REST API)
• Conditional updates - When fetching the Markdown source, it will store the ETag from the server, and send it back on the next request. GitHub will return a 304 response, allowing us to skip updates altogether.
• Simplified manifest - Removed the requirement for title and cmd_path from the manifest. title is pulled from Markdown anyway, and cmd_path is redundant with the key already there. (This still correctly parses the CLI command manifest.)

Will also publish this to GitHub as a standalone plugin.

[rmccue]

Now available on GitHub: ​https://github.com/WP-API/markdown-sync

[rmccue]

Updated patch with admin UI

[rmccue]

Added 2968.2.diff​ which changes the following:

• Edit Links - Changes admin bar Edit link to point at GitHub, and adds an edit link after the page title for all users.
• Admin UI - Adds a message to editors who go to the page warning that content/title/slug are synced.
• No CLI Changes - I removed the CLI command reference changes here, so we can ship for the API handbook without being blocked on compatibility. That said, I still have the changes ready, and it'd be great to switch both (and also the regular CLI handbook) eventually.

I'm personally happy to ship this ASAP, since we want to keep making content changes, and I want to avoid a messy reimport to Markdown (which I did by hand).

@kadamwhite Are you happy for us to switch over? If so, let's wrangle a meta-committer and get this thing shipped.

[rmccue]

Parse Markdown inside shortcodes

[rmccue]

2968.3.diff​ allows Markdown inside shortcodes. This is handy for things like [alert], and also works around ​https://github.com/Automattic/jetpack/issues/7535

[kadamwhite]

Going to review this today and then would be down to move forward!

[kadamwhite]

When this patch is applied the plugin will not be active yet (because it's being added), and if the plugin is not active then we get an error Class 'WordPressdotorg\Markdown\Importer' not found. Should we have a defensive check around this?

[rmccue]

Should we have a defensive check around this?

Makes sense to me! I'll update the patch with this.

[rmccue]

Wrap REST API class include in class_exists

[rmccue]

Prefix cron actions with devhub_ and ensure schedule is registered

[kadamwhite]

Patch applies cleanly, works as advertised, and this would be a huge win. +1 from me!

[rmccue]

Let's ship it.

[Otto42]

[5992] Add wporg-markdown plugin from #2968. This does not make it live on w.org yet, this is only preliminary. More commits to follow.

[Otto42]

In 5993:

Devhub: Add changes to use wporg-markdown code from developer theme. Props @rmccue, fixes #2968.