Add methods to dart:io Path.

runtime/bin/path.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * A Path, which is a String interpreted as a sequence of path segments,
  * which are strings, separated by forward slashes.
  * Paths are immutable wrappers of a String, that offer member functions for
  * useful path manipulations and queries.  Joining of paths and normalization
  * interpret '.' and '..' in the usual way.
@@ skipping 105 matching lines @@
    * path separator do not have leading or terminating empty segments.
    * Other than that, the segments are just the result of splitting the
    * path on the path separator.
    *
    *     new Path('/a/b/c/d').segments() == ['a', 'b', 'c', d'];
    *     new Path(' foo bar //../') == [' foo bar ', '', '..'];
    */
   List<String> segments();
 
   /**
+   * Appends [finalSegment] to a path as a new segment.  Adds a path separator
+   * between the path and [finalSegment] if the path does not already end in
+   * a path separator.  The path is not canonicalized, and [finalSegment] may
+   * contain path separators.
+   */
+  Path append(String finalSegment);
+
+  /**
    * Drops the final path separator and whatever follows it from this Path,
    * and returns the resulting Path object.  If the only path separator in
    * this Path is the first character, returns '/' instead of the empty string.
    * If there is no path separator in the Path, returns the empty string.
    *
    *     new Path('../images/dot.gif').directoryPath == '../images'
    *     new Path('/usr/geoffrey/www/').directoryPath == '/usr/geoffrey/www'
    *     new Path('lost_file_old').directoryPath == ''
    *     new Path('/src').directoryPath == '/'
    *     Note: new Path('/D:/src').directoryPath == '/D:'
    */
   Path get directoryPath();
 
   /**
    * The part of the path after the last path separator, or the entire path if
    * it contains no path separator.
    *
    *     new Path('images/DSC_0027.jpg).filename == 'DSC_0027.jpg'
    *     new Path('users/fred/').filename == ''
    */
   String get filename();
 
   /**
    * The part of [filename] before the last '.', or the entire filename if it
-   * contains no '.'.
+   * contains no '.'.  If [filename] is '.' or '..' it is unchanged.
    *
    *     new Path('/c:/My Documents/Heidi.txt').filenameWithoutExtension
    *     would return 'Heidi'.
    *     new Path('not what I would call a path').filenameWithoutExtension
    *     would return 'not what I would call a path'.
    */
   String get filenameWithoutExtension();
 
   /**
    * The part of [filename] after the last '.', or '' if [filename]
-   * contains no '.'.
+   * contains no '.'.  If [filename] is '.' or '..', returns ''.
    *
    *     new Path('tiger.svg').extension == 'svg'
    *     new Path('/src/dart/dart_secrets').extension == ''
    */
   String get extension();
 }