GN: Change gen command syntax, support relative dirs.

base/files/file_path.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // FilePath is a container for pathnames stored in a platform's native string
 // type, providing containers for manipulation in according with the
 // platform's conventions for pathnames.  It supports the following path
 // types:
 //
 //                   POSIX            Windows
@@ skipping 171 matching lines @@
   bool empty() const { return path_.empty(); }
 
   void clear() { path_.clear(); }
 
   // Returns true if |character| is in kSeparators.
   static bool IsSeparator(CharType character);
 
   // Returns a vector of all of the components of the provided path. It is
   // equivalent to calling DirName().value() on the path's root component,
   // and BaseName().value() on each child component.
+  //
+  // To make sure this is lossless so we can differentiate absolute and
+  // relative paths, the root slash will be included even though no other
+  // slashes will be. The precise behavior is:
+  //
+  // Posix:  "/foo/bar"  ->  [ "/", "foo", "bar" ]
+  // Windows:  "C:\foo\bar"  ->  [ "C:", "\\", "foo", "bar" ]
   void GetComponents(std::vector<FilePath::StringType>* components) const;
 
   // Returns true if this FilePath is a strict parent of the |child|. Absolute
   // and relative paths are accepted i.e. is /foo parent to /foo/bar and
   // is foo parent to foo/bar. Does not convert paths to absolute, follow
   // symlinks or directory navigation (e.g. ".."). A path is *NOT* its own
   // parent.
   bool IsParent(const FilePath& child) const;
 
   // If IsParent(child) holds, appends to path (if non-NULL) the
@@ skipping 253 matching lines @@
 
 inline size_t hash_value(const base::FilePath& f) {
   return hash_value(f.value());
 }
 
 #endif  // COMPILER
 
 }  // namespace BASE_HASH_NAMESPACE
 
 #endif  // BASE_FILES_FILE_PATH_H_