Upgrade/Install: Display "You are using a development version" message in the admin footer for Beta or RC versions.

This ensures that the message is displayed when the `WP_AUTO_UPDATE_CORE` constant is set to `beta` or `rc` and the user is on a development version.

Props afragen.
Reviewed by azaozz, SergeyBiryukov.
Merges [49708] to the 5.6 branch.
Fixes #51892.
Built from https://develop.svn.wordpress.org/branches/5.6@49711


git-svn-id: http://core.svn.wordpress.org/branches/5.6@49434 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/update.php

@@ -248,6 +248,12 @@ function core_update_footer( $msg = '' ) {
 		$cur->response = '';
 	}
 
+	$is_development_version = preg_match( '/alpha|beta|RC/', $cur->version );
+
+	if ( $is_development_version && 'latest' === $cur->response ) {
+		$cur->response = 'development';
+	}
+
 	switch ( $cur->response ) {
 		case 'development':
 			return sprintf(

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.6-RC1-49707';
+$wp_version = '5.6-RC1-49711';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.