Clean up some warnings and deprecated calls.

utils/pub/git.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.
 
 /// Helper functionality for invoking Git.
 library git;
 
 import 'dart:async';
 import 'io.dart';
 import 'log.dart' as log;
@@ skipping 10 matching lines @@
 
 /// Run a git process with [args] from [workingDir]. Returns the stdout as a
 /// list of strings if it succeeded. Completes to an exception if it failed.
 Future<List<String>> run(List<String> args,
     {String workingDir, Map<String, String> environment}) {
   return _gitCommand.then((git) {
     return runProcess(git, args, workingDir: workingDir,
         environment: environment);
   }).then((result) {
     if (!result.success) throw new Exception(
-        'Git error. Command: git ${Strings.join(args, " ")}\n'
-        '${Strings.join(result.stderr, "\n")}');
+        'Git error. Command: git ${args.join(" ")}\n'
+        '${result.stderr.join("\n")}');
 
     return result.stdout;
   });
 }
 
 bool _isGitInstalledCache;
 
 /// The cached Git command.
 String _gitCommandCache;
 
@@ skipping 23 matching lines @@
 Future<bool> _tryGitCommand(String command) {
   // If "git --version" prints something familiar, git is working.
   return runProcess(command, ["--version"]).then((results) {
     var regexp = new RegExp("^git version");
     return results.stdout.length == 1 && regexp.hasMatch(results.stdout[0]);
   }).catchError((err) {
     // If the process failed, they probably don't have it.
     return false;
   });
 }