Show partial reports in pub get, serve, and build.

sdk/lib/_internal/pub/test/pub_test.dart

Index: sdk/lib/_internal/pub/test/pub_test.dart
diff --git a/sdk/lib/_internal/pub/test/pub_test.dart b/sdk/lib/_internal/pub/test/pub_test.dart
index 80d4dc848d090fd07c0865ffcd6cc3674b089757..585b3f4eca29f03c0f92ac9bb72199227911a1ea 100644
--- a/sdk/lib/_internal/pub/test/pub_test.dart
+++ b/sdk/lib/_internal/pub/test/pub_test.dart
@@ -70,6 +70,7 @@ main() {
           Usage: pub get
           -h, --help            Print usage information for this command.
               --[no-]offline    Use cached packages instead of accessing the network.
+          -n, --dry-run         Report what dependencies would change but don't change any.
     ''');
   });
 
@@ -81,6 +82,7 @@ main() {
           Usage: pub get
           -h, --help            Print usage information for this command.
               --[no-]offline    Use cached packages instead of accessing the network.
+          -n, --dry-run         Report what dependencies would change but don't change any.
     ''');
   });
 
@@ -199,6 +201,7 @@ main() {
             Usage: pub get
             -h, --help            Print usage information for this command.
                 --[no-]offline    Use cached packages instead of accessing the network.
+            -n, --dry-run         Report what dependencies would change but don't change any.
             ''');
     });