[GN] Add support to rebase_path to resolve paths above the source root.

tools/gn/function_rebase_path_unittest.cc

 // Copyright (c) 2013 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.
 
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/functions.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/test_with_scope.h"
 
@@ skipping 25 matching lines @@
   Scope* scope = setup.scope();
   scope->set_source_dir(SourceDir("//tools/gn/"));
 
   // Build-file relative paths.
   EXPECT_EQ("../../tools/gn", RebaseOne(scope, ".", "//out/Debug", "."));
   EXPECT_EQ("../../tools/gn/", RebaseOne(scope, "./", "//out/Debug", "."));
   EXPECT_EQ("../../tools/gn/foo", RebaseOne(scope, "foo", "//out/Debug", "."));
   EXPECT_EQ("../..", RebaseOne(scope, "../..", "//out/Debug", "."));
   EXPECT_EQ("../../", RebaseOne(scope, "../../", "//out/Debug", "."));
 
-  // We don't allow going above the root source dir.
+  // Without a source root defined, we cannot move out of the source tree.
   EXPECT_EQ("../..", RebaseOne(scope, "../../..", "//out/Debug", "."));
 
   // Source-absolute input paths.
   EXPECT_EQ("./", RebaseOne(scope, "//", "//", "//"));
   EXPECT_EQ("foo", RebaseOne(scope, "//foo", "//", "//"));
   EXPECT_EQ("foo/", RebaseOne(scope, "//foo/", "//", "//"));
   EXPECT_EQ("../../foo/bar", RebaseOne(scope, "//foo/bar", "//out/Debug", "."));
   EXPECT_EQ("./", RebaseOne(scope, "//foo/", "//foo/", "//"));
   // Thie one is technically correct but could be simplified to "." if
   // necessary.
   EXPECT_EQ("../foo", RebaseOne(scope, "//foo", "//foo", "//"));
 
   // Test slash conversion.
   EXPECT_EQ("foo/bar", RebaseOne(scope, "foo/bar", ".", "."));
   EXPECT_EQ("foo/bar", RebaseOne(scope, "foo\\bar", ".", "."));
 
   // Test system path output.
 #if defined(OS_WIN)
-  setup.build_settings()->SetRootPath(base::FilePath(L"C:/source"));
-  EXPECT_EQ("C:/source", RebaseOne(scope, ".", "", "//"));
-  EXPECT_EQ("C:/source/", RebaseOne(scope, "//", "", "//"));
-  EXPECT_EQ("C:/source/foo", RebaseOne(scope, "foo", "", "//"));
-  EXPECT_EQ("C:/source/foo/", RebaseOne(scope, "foo/", "", "//"));
-  EXPECT_EQ("C:/source/tools/gn/foo", RebaseOne(scope, "foo", "", "."));
+  setup.build_settings()->SetRootPath(base::FilePath(L"C:/path/to/src"));
+  EXPECT_EQ("C:/path/to/src", RebaseOne(scope, ".", "", "//"));
+  EXPECT_EQ("C:/path/to/src/", RebaseOne(scope, "//", "", "//"));
+  EXPECT_EQ("C:/path/to/src/foo", RebaseOne(scope, "foo", "", "//"));
+  EXPECT_EQ("C:/path/to/src/foo/", RebaseOne(scope, "foo/", "", "//"));
+  EXPECT_EQ("C:/path/to/src/tools/gn/foo", RebaseOne(scope, "foo", "", "."));
+  EXPECT_EQ("C:/path/to/other/tools",
+            RebaseOne(scope, "//../other/tools", "", "//"));
+  EXPECT_EQ("C:/path/to/src/foo/bar",
+            RebaseOne(scope, "//../src/foo/bar", "", "//"));
+  EXPECT_EQ("C:/path/to", RebaseOne(scope, "//..", "", "//"));
+  EXPECT_EQ("C:/path", RebaseOne(scope, "../../../..", "", "."));
+  EXPECT_EQ("C:/path/to/external/dir/",
+            RebaseOne(scope, "//../external/dir/", "", "//"));
+
 #else
-  setup.build_settings()->SetRootPath(base::FilePath("/source"));
-  EXPECT_EQ("/source", RebaseOne(scope, ".", "", "//"));
-  EXPECT_EQ("/source/", RebaseOne(scope, "//", "", "//"));
-  EXPECT_EQ("/source/foo", RebaseOne(scope, "foo", "", "//"));
-  EXPECT_EQ("/source/foo/", RebaseOne(scope, "foo/", "", "//"));
-  EXPECT_EQ("/source/tools/gn/foo", RebaseOne(scope, "foo", "", "."));
+  setup.build_settings()->SetRootPath(base::FilePath("/path/to/src"));
+  EXPECT_EQ("/path/to/src", RebaseOne(scope, ".", "", "//"));
+  EXPECT_EQ("/path/to/src/", RebaseOne(scope, "//", "", "//"));
+  EXPECT_EQ("/path/to/src/foo", RebaseOne(scope, "foo", "", "//"));
+  EXPECT_EQ("/path/to/src/foo/", RebaseOne(scope, "foo/", "", "//"));
+  EXPECT_EQ("/path/to/src/tools/gn/foo", RebaseOne(scope, "foo", "", "."));
+  EXPECT_EQ("/path/to/other/tools",
+            RebaseOne(scope, "//../other/tools", "", "//"));
+  EXPECT_EQ("/path/to/src/foo/bar",
+            RebaseOne(scope, "//../src/foo/bar", "", "//"));
+  EXPECT_EQ("/path/to", RebaseOne(scope, "//..", "", "//"));
+  EXPECT_EQ("/path", RebaseOne(scope, "../../../..", "", "."));
+  EXPECT_EQ("/path/to/external/dir/",
+            RebaseOne(scope, "//../external/dir/", "", "//"));
 #endif
 }
 
 TEST(RebasePath, StringsSystemPaths) {
   TestWithScope setup;
   Scope* scope = setup.scope();
 
 #if defined(OS_WIN)
   setup.build_settings()->SetBuildDir(SourceDir("C:/ssd/out/Debug"));
   setup.build_settings()->SetRootPath(base::FilePath(L"C:/hdd/src"));
@@ skipping 72 matching lines @@
   TestWithScope setup;
   setup.build_settings()->SetBuildDir(SourceDir("//out/Debug/"));
 
   // No arg input should issue an error.
   Err err;
   std::vector<Value> args;
   FunctionCallNode function;
   Value ret = functions::RunRebasePath(setup.scope(), &function, args, &err);
   EXPECT_TRUE(err.has_error());
 }