Make the ninja generator handle symlinked paths correctly.

test/symlinks/gyptest-symlinks.py

Index: test/symlinks/gyptest-symlinks.py
diff --git a/test/symlinks/gyptest-symlinks.py b/test/symlinks/gyptest-symlinks.py
new file mode 100755
index 0000000000000000000000000000000000000000..5b4ad16a9d4174543f300607e02325a434bc1ba0
--- /dev/null
+++ b/test/symlinks/gyptest-symlinks.py
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+
+# Copyright (c) 2015 Google Inc. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+Test that RelativePath(s, d) doesn't return a path starting with '..' when
+s is textually below d, but is also a symlink to a file that is not below d.
+
+Returning .. in this case would break the Ninja generator in such a case,
+because it computes output directories by concatenating paths, and concat'ing
+a path starting with .. can unexpectedly erase other parts of the path. It's
+difficult to test this directly since the test harness assumes toplevel_dir is
+the root of the repository, but this test should at least verify that the
+required behavior doesn't change.
+"""
+
+import TestGyp
+import os
+import sys
+import tempfile
+
+if sys.platform != 'win32':
+  test = TestGyp.TestGyp()
+
+  # Copy hello.gyp and hello.c to temporary named files, which will then be
+  # symlinked back and processed. Note that we don't ask gyp to touch the
+  # original files at all; they are only there as source material for the copy.
+  # That's why hello.gyp references symlink_hello.c instead of hello.c.
+  with tempfile.NamedTemporaryFile() as gyp_file:
+    with tempfile.NamedTemporaryFile() as c_file:
+      with open('hello.gyp') as orig_gyp_file:
+        gyp_file.write(orig_gyp_file.read())
+        gyp_file.flush()
+      with open('hello.c') as orig_c_file:
+        c_file.write(orig_c_file.read())
+        c_file.flush()
+      # We need to flush the files because we want to read them before closing
+      # them, since when they are closed they will be deleted.
+
+      # Don't proceed with the test on a system that doesn't let you read from
+      # a still-open temporary file.
+      if os.path.getsize(gyp_file.name) == 0:
+        raise OSError("Copy to temporary file didn't work.")
+
+      symlink_gyp = test.built_file_path('symlink_hello.gyp')
+      symlink_c = test.built_file_path('symlink_hello.c')
+      outdir = os.path.dirname(symlink_gyp)
+
+      # Make sure the outdir exists.
+      try:
+        os.makedirs(outdir)
+      except OSError:
+        if not os.path.isdir(outdir):
+          raise
+      os.symlink(gyp_file.name, symlink_gyp)
+      os.symlink(c_file.name, symlink_c)
+
+      # Run gyp on the symlinked files.
+      test.run_gyp(symlink_gyp, chdir=outdir)
+      test.build(symlink_gyp, chdir=outdir)
+      test.run_built_executable('symlink_hello', stdout="Hello, world!\n",
+                                chdir=outdir)
+
+      test.pass_test()
+