Start pulling pub from its own repo.

sdk/lib/_internal/pub/lib/src/sdk.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.
-
-/// Operations relative to the user's installed Dart SDK.
-library pub.sdk;
-
-import 'dart:io';
-
-import 'package:path/path.dart' as path;
-import 'package:pub_semver/pub_semver.dart';
-
-import 'io.dart';
-
-/// Gets the path to the root directory of the SDK.
-///
-/// When running from the actual built SDK, this will be the SDK that contains
-/// the running Dart executable. When running from the repo, it will be the
-/// "sdk" directory in the Dart repository itself.
-final String rootDirectory =
-    runningFromSdk ? _rootDirectory : path.join(repoRoot, "sdk");
-
-/// Gets the path to the root directory of the SDK, assuming that the currently
-/// running Dart executable is within it.
-final String _rootDirectory =
-    path.dirname(path.dirname(Platform.executable));
-
-/// The SDK's revision number formatted to be a semantic version.
-///
-/// This can be set so that the version solver tests can artificially select
-/// different SDK versions.
-Version version = _getVersion();
-
-/// Determine the SDK's version number.
-Version _getVersion() {
-  // Some of the pub integration tests require an SDK version number, but the
-  // tests on the bots are not run from a built SDK so this lets us avoid
-  // parsing the missing version file.
-  var sdkVersion = Platform.environment["_PUB_TEST_SDK_VERSION"];
-  if (sdkVersion != null) return new Version.parse(sdkVersion);
-
-  if (runningFromSdk) {
-    // Read the "version" file.
-    var version = readTextFile(path.join(_rootDirectory, "version")).trim();
-    return new Version.parse(version);
-  }
-
-  // When running from the repo, read the canonical VERSION file in tools/.
-  // This makes it possible to run pub without having built the SDK first.
-  var contents = readTextFile(path.join(repoRoot, "tools/VERSION"));
-
-  parseField(name) {
-    var pattern = new RegExp("^$name ([a-z0-9]+)", multiLine: true);
-    var match = pattern.firstMatch(contents);
-    return match[1];
-  }
-
-  var channel = parseField("CHANNEL");
-  var major = parseField("MAJOR");
-  var minor = parseField("MINOR");
-  var patch = parseField("PATCH");
-  var prerelease = parseField("PRERELEASE");
-  var prereleasePatch = parseField("PRERELEASE_PATCH");
-
-  var version = "$major.$minor.$patch";
-  if (channel == "be") {
-    // TODO(rnystrom): tools/utils.py includes the svn commit here. Should we?
-    version += "-edge";
-  } else if (channel == "dev") {
-    version += "-dev.$prerelease.$prereleasePatch";
-  }
-
-  return new Version.parse(version);
-}