Explicitly configure git committer.

utils/pub/io.dart

Index: utils/pub/io.dart
diff --git a/utils/pub/io.dart b/utils/pub/io.dart
index c2f14568906fd92033c75fdd9e71d1b2c4990d43..13de28191687c4a2eb180b05de6a09d771336c05 100644
--- a/utils/pub/io.dart
+++ b/utils/pub/io.dart
@@ -471,15 +471,17 @@ Future<List<int>> consumeInputStream(InputStream stream) {
   return completer.future;
 }
 
-/**
- * Spawns and runs the process located at [executable], passing in [args].
- * Returns a [Future] that will complete the results of the process after it
- * has ended.
- *
- * If [pipeStdout] and/or [pipeStderr] are set, all output from the subprocess's
- * output streams are sent to the parent process's output streams. Output from
- * piped streams won't be available in the result object.
- */
+/// Spawns and runs the process located at [executable], passing in [args].
+/// Returns a [Future] that will complete the results of the process after it
+/// has ended.
+///
+/// The spawned process will inherit its parents environment variables. If
+/// [environment] is provided, that will be used to augment (not replace) the
+/// the inherited variables.
+///
+/// If [pipeStdout] and/or [pipeStderr] are set, all output from the
+/// subprocess's output streams are sent to the parent process's output streams.
+/// Output from piped streams won't be available in the result object.
 Future<PubProcessResult> runProcess(String executable, List<String> args,
     {workingDir, Map<String, String> environment, bool pipeStdout: false,
     bool pipeStderr: false}) {
@@ -499,7 +501,11 @@ Future<PubProcessResult> runProcess(String executable, List<String> args,
   if (workingDir != null) {
     options.workingDirectory = _getDirectory(workingDir).path;
   }
-  options.environment = environment;
+
+  if (environment != null) {
+    options.environment = new Map.from(Platform.environment);
+    environment.forEach((key, value) => options.environment[key] = value);
+  }
 
   var future = Process.run(executable, args, options);
   return future.transform((result) {
@@ -556,8 +562,11 @@ Future<bool> get isGitInstalled {
 }
 
 /// Run a git process with [args] from [workingDir].
-Future<PubProcessResult> runGit(List<String> args, {String workingDir}) =>
-    _gitCommand.chain((git) => runProcess(git, args, workingDir: workingDir));
+Future<PubProcessResult> runGit(List<String> args,
+    {String workingDir, Map<String, String> environment}) {
+  return _gitCommand.chain((git) => runProcess(git, args,
+        workingDir: workingDir, environment: environment));
+}
 
 /// Returns the name of the git command-line app, or null if Git could not be
 /// found on the user's PATH.