Markdown: enable for posts whenever the module is active. (#6608)

* Markdown: enable for posts whenever the module is active.

Also remove the option from Settings > Writing.

Fixes #6605

Related:
- #6406
- #6548

* Markdown: make sure posts markdown is re-enabled on upgrade

* Remove setting checkbox from writing options page

class.jetpack.php

@@ -349,6 +349,11 @@ function plugin_upgrade() {
 					Jetpack_Options::delete_option( 'identity_crisis_whitelist' );
 				}
 
+				// Make sure Markdown for posts gets turned back on
+				if ( ! get_option( 'wpcom_publish_posts_with_markdown' ) ) {
+					update_option( 'wpcom_publish_posts_with_markdown', true );
+				}
+
 				Jetpack::maybe_set_version_option();
 			}
 		}

modules/markdown.php

@@ -13,3 +13,17 @@
  */
 
 include dirname( __FILE__ ) . '/markdown/easy-markdown.php';
+
+/**
+ * Remove checkbox set in modules/markdown/easy-markdown.php.
+ * We don't just remove the register_setting call there because the checkbox is
+ * needed on WordPress.com, where the file is sync'ed verbatim.
+ */
+function jetpack_markdown_posting_always_on() {
+	// why oh why isn't there a remove_settings_field?
+	global $wp_settings_fields;
+	if ( isset( $wp_settings_fields['writing']['default'][ WPCom_Markdown::POST_OPTION ] ) ) {
+		unset( $wp_settings_fields['writing']['default'][ WPCom_Markdown::POST_OPTION ] );
+	}
+}
+add_action( 'admin_init', 'jetpack_markdown_posting_always_on', 11 );