Add a Pub source that checks packages out from Git.

utils/pub/io.dart

Index: utils/pub/io.dart
diff --git a/utils/pub/io.dart b/utils/pub/io.dart
index 7a6357080490b5d08a57f8b03bea855fa020c1ef..ac9836af5078e2e40ed4f6496376f3bc5fd31e5d 100644
--- a/utils/pub/io.dart
+++ b/utils/pub/io.dart
@@ -258,9 +258,13 @@ String getFullPath(entry) => new File(_getPath(entry)).fullPathSync();
  * 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.
  */
 Future<PubProcessResult> runProcess(String executable, List<String> args,
-    [String workingDir]) {
+    [String workingDir, bool pipeStdout = false, bool pipeStderr = false]) {
   int exitCode;
 
   final options = new ProcessOptions();
@@ -278,21 +282,29 @@ Future<PubProcessResult> runProcess(String executable, List<String> args,
 
   checkComplete() {
     // Wait until the process is done and its output streams are closed.
-    if (!outStream.closed) return;
-    if (!errStream.closed) return;
+    if (!pipeStdout && !outStream.closed) return;
+    if (!pipeStderr && !errStream.closed) return;
     if (exitCode == null) return;
 
     completer.complete(new PubProcessResult(
         processStdout, processStderr, exitCode));
   }
 
-  outStream.onLine   = () => processStdout.add(outStream.readLine());
-  outStream.onClosed = checkComplete;
-  outStream.onError  = (error) => completer.completeException(error);
+  if (pipeStdout) {
+    process.stdout.pipe(stdout, close: false);
+  } else {
+    outStream.onLine   = () => processStdout.add(outStream.readLine());
+    outStream.onClosed = checkComplete;
+    outStream.onError  = (error) => completer.completeException(error);
+  }
 
-  errStream.onLine   = () => processStderr.add(errStream.readLine());
-  errStream.onClosed = checkComplete;
-  errStream.onError  = (error) => completer.completeException(error);
+  if (pipeStderr) {
+    process.stderr.pipe(stderr, close: false);
+  } else {
+    errStream.onLine   = () => processStderr.add(errStream.readLine());
+    errStream.onClosed = checkComplete;
+    errStream.onError  = (error) => completer.completeException(error);
+  }
 
   process.onExit = (actualExitCode) {
     exitCode = actualExitCode;
@@ -313,6 +325,8 @@ class PubProcessResult {
   final int exitCode;
 
   const PubProcessResult(this.stdout, this.stderr, this.exitCode);
+
+  bool get success() => exitCode == 0;
 }
 
 /**