Add a line to pub usage output explaining how to see global options.

sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart

Index: sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart
diff --git a/sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart b/sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart
index 81f3a51a12aea14c59925dbb30cdd42f0e0ebed7..44de5f40732218173ab62b99cbe83b1acbf96464 100644
--- a/sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart
+++ b/sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart
@@ -26,6 +26,8 @@ Can not run an executable in a subdirectory of a dependency.
 
 Usage: pub run <executable> [args...]
 -h, --help    Print usage information for this command.
+
+Run "pub help" to see global options.
 """,
         exitCode: exit_codes.USAGE);
   });