Look for git.cmd on Windows.

utils/tests/pub/test_pub.dart

Index: utils/tests/pub/test_pub.dart
diff --git a/utils/tests/pub/test_pub.dart b/utils/tests/pub/test_pub.dart
index 08b3e178e8ac410e0ba5b1a46e0fd6ff7f645e35..e6a972b6403c08cd66c1a5cdfe00db044fdb519a 100644
--- a/utils/tests/pub/test_pub.dart
+++ b/utils/tests/pub/test_pub.dart
@@ -983,11 +983,10 @@ class GitRepoDescriptor extends DirectoryDescriptor {
   }
 
   Future<String> _runGit(List<String> args, Directory workingDir) {
-    return runProcess('git', args, workingDir: workingDir.path).
-      transform((result) {
-        if (!result.success) throw "Error running git: ${result.stderr}";
-        return result.stdout;
-      });
+    return runGit(args, workingDir: workingDir.path).transform((result) {
+      if (!result.success) throw "Error running git: ${result.stderr}";
+      return result.stdout;
+    });
   }
 }