WP_Filesystem: SSH2 handler: Remove support for is_writable() via SSH, it turns out PHP doesn't verify the writability via SFTP and instead uses a comparison based on the current php system process user instead of the ssh user.

This fixes the 'The update cannot be installed because we will be unable to copy some files.' error encountered during updates by skipping the write test completely.

Props jobst.
Fixes #33480 for trunk

Built from https://develop.svn.wordpress.org/trunk@33688


git-svn-id: http://core.svn.wordpress.org/trunk@33655 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-filesystem-ssh2.php

@@ -383,8 +383,8 @@ class WP_Filesystem_SSH2 extends WP_Filesystem_Base {
 	 * @return bool
 	 */
 	public function is_writable($file) {
-		$file = ltrim($file, '/');
-		return is_writable('ssh2.sftp://' . $this->sftp_link . '/' . $file);
+		// PHP will base it's writable checks on system_user === file_owner, not ssh_user === file_owner
+		return true;
 	}
 	/**
 	 * @param string $file

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-33687';
+$wp_version = '4.4-alpha-33688';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.