Direct sync

[paulsonnentag]

The current implementation of automerge-codemirror inverts Codemirror transactions to sync the state with an Automerge document, which breaks the history plugin of Codemirror. This was a performance optimization, so we don't need to create a new change for each keystroke and instead can batch multiple keystrokes together. This optimization is no longer necessary because Automerge is fast enough.

This new implementation simplifies this by changing the automerge document directly on each keystroke and remembering the resulting heads. If a remote change comes in, we diff the new version against the stored heads and apply the patches to automerge

I'm also simplifying the API. automerge-codemirror is just a single Codemirror plugin now and doesn't need any external setup anymore. The only thing you need to do is set the initial source to the value of the document at initialization

const source = handle.docSync()
const view = new EditorView({
  doc: source,
  extensions: [
    basicSetup,
    automergeSyncPlugin({
      handle,
      path: ["text"],
    }),
  ],
  parent: containerRef.current,
}))

[alexjg]

Overall looks great, enormously simplifies things!

The only thing I think this PR needs is an assertion in the cypress tests that after all the undo/redo stuff has happened the state of the document (automerge document that is) is what we would expect.

[paulsonnentag]

That's a good point. I will add that