try to clarify why it is upgrading dependents

[rdp]

• [ x] Have you followed the guidelines in our Contributing document?
• [x ] Have you checked to ensure there aren't other open Pull Requests for the same change?
• [x ] Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example. There weren't any close tempates to model after.
• [x ] Have you successfully run brew style with your changes locally?
• [ x] Have you successfully run brew typecheck with your changes locally?
• [ x] Have you successfully run brew tests with your changes locally? Though unclear since terminal line endings get mixed up?

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The motivation for this is: if I update "x" brew might update seemingly unrelated apps (that aren't even dependencies), try and clarify why it does that. Suggestions welcome!

Homebrew/discussions#2179 (reply in thread)

[MikeMcQuaid]

Looks good so far but needs some style tweaks.

[rdp]

Oops, those look good, thanks!

[MikeMcQuaid]

Thanks again @rdp!