Only modify the tasks that would be listed if "mod" was not supplied

#### To request a feature...

* Clearly describe the feature:
When I want to batch modify, I want to quickly verify that I won't corrupt my tasks because batch operations can't be undo.

* Clearly state the use case. We are only interested in use cases, do not waste time with implementation details or suggested syntax.

use case: add to a project "holidays" all the tasks (8) with a description that begins with "holidays:"

1. `task /holidays:/` return 8 tasks, I quickly scans them to verify that there are the exact tasks that I want to modify
2. `task /holidays:/ mod pro:holidays` modify exactly these 8 tasks

* Please see our notes on [How to request a feature](https://taskwarrior.org/docs/features.html)
I don't often batch process tasks, but when I do, I am always afraid that I would break anything.