Make short-running Git operations synchronous.

sdk/lib/_internal/pub/lib/src/source/git.dart

Index: sdk/lib/_internal/pub/lib/src/source/git.dart
diff --git a/sdk/lib/_internal/pub/lib/src/source/git.dart b/sdk/lib/_internal/pub/lib/src/source/git.dart
index b0488c4ebbe14d6413c5946fdb94f8ca3cc32fb3..c0aa95d668ce626d4b89d8fd206e79c2c232615c 100644
--- a/sdk/lib/_internal/pub/lib/src/source/git.dart
+++ b/sdk/lib/_internal/pub/lib/src/source/git.dart
@@ -51,16 +51,14 @@ class GitSource extends CachedSource {
 
     var revisionCachePath;
 
-    return git.isInstalled.then((installed) {
-      if (!installed) {
-        throw new ApplicationException(
-            "Cannot get ${id.name} from Git (${_getUrl(id)}).\n"
-            "Please ensure Git is correctly installed.");
-      }
+    if (!git.isInstalled) {
+      throw new ApplicationException(
+          "Cannot get ${id.name} from Git (${_getUrl(id)}).\n"
+          "Please ensure Git is correctly installed.");
+    }
 
-      ensureDir(path.join(systemCacheRoot, 'cache'));
-      return _ensureRevision(id);
-    }).then((_) => getDirectory(id)).then((path) {
+    ensureDir(path.join(systemCacheRoot, 'cache'));
+    return _ensureRevision(id).then((_) => getDirectory(id)).then((path) {
       revisionCachePath = path;
       if (entryExists(revisionCachePath)) return null;
       return _clone(_repoCachePath(id), revisionCachePath, mirror: false);