When autosaving drafts, don't create revisions.

editor/actions.js

@@ -234,9 +234,10 @@ export function editPost( edits ) {
 	};
 }
 
-export function savePost() {
+export function savePost( options ) {
 	return {
 		type: 'REQUEST_POST_UPDATE',
+		options,
 	};
 }
 

editor/effects.js

@@ -17,6 +17,7 @@ import {
 	getDefaultBlockName,
 } from '@wordpress/blocks';
 import { __ } from '@wordpress/i18n';
+import { addQueryArgs } from '@wordpress/url';
 
 /**
  * Internal dependencies
@@ -76,7 +77,13 @@ export default {
 		} );
 		dispatch( removeNotice( SAVE_POST_NOTICE_ID ) );
 		const Model = wp.api.getPostTypeModel( getCurrentPostType( state ) );
-		new Model( toSend ).save().done( ( newPost ) => {
+		const newModel = new Model( toSend );
+
+		// Tag the autosave action to avoid creating revisions.
+		if ( action.options && action.options.autosave ) {
+			newModel.url = addQueryArgs( newModel.url(), { 'gutenberg_autosave': '1' } );
+		}
+		newModel.save().done( ( newPost ) => {
 			dispatch( {
 				type: 'RESET_POST',
 				post: newPost,
@@ -278,7 +285,7 @@ export default {
 			dispatch( editPost( { status: 'draft' } ) );
 		}
 
-		dispatch( savePost() );
+		dispatch( savePost( { 'autosave': 1 } ) );
 	},
 	SETUP_EDITOR( action ) {
 		const { post, settings } = action;

gutenberg.php

@@ -545,3 +545,19 @@ function gutenberg_replace_default_add_new_button() {
 function gutenberg_add_admin_body_class( $classes ) {
 	return "$classes gutenberg-editor-page";
 }
+
+/**
+ * Filter the number of revisions for posts, skipping revisions when autosaving.
+ *
+ * @param  int $count The number of revisions to save.
+ *
+ * @return int        The original count, or zero if this is a Gutenberg autosave.
+ */
+function gutenberg_filter_revisions( $count ) {
+
+	if ( isset( $_REQUEST['gutenberg_autosave'] ) && '1' === $_REQUEST['gutenberg_autosave'] ) {
+		return 0;
+	}
+	return $count;
+}
+add_filter( 'wp_revisions_to_keep', 'gutenberg_filter_revisions' );