Allow casks to opt-in to forcibly quit during brew upgrade

[setchy]

Verification

• This issue's title and/or description do not reference a single formula e.g. brew install wget. If they do, open an issue at https://github.com/Homebrew/homebrew-core/issues/new/choose instead.

Provide a detailed description of the proposed feature

Currently when performing brew upgrade, the quit stanza is skipped.

This FR is to add the ability for cask maintainers to opt-in to forcibly quit before upgrading their apps.

What is the motivation for the feature?

Based on feedback from @bevanjkay on Homebrew/homebrew-cask#173061

In the instance of Gitify, users experience errors/exceptions when the application is upgraded in-place without exiting it first

How will the feature be relevant to at least 90% of Homebrew users?

to be discussed

What alternatives to the feature have been considered?

Adding custom preflight and postflight scripts to individual casks

[MikeMcQuaid]

Seems reasonable to me but defer to @Homebrew/cask folks.

[bevanjkay]

skipping these stanzas (uninstall quit, and uninstall signal) was a recent change, because apps such as Visual Studio Code should not be forcibly closed as it is likely to cause a loss of work. And we were seeing an increase in PRs to add the stanzas.

Adding the ability to specify that the stanza should fire on upgrade makes sense to me, but the criteria for when this should apply could be difficult to determine. I would suggest that the loss of work is the item that matters most.

[MikeMcQuaid]

Adding the ability to specify that the stanza should fire on upgrade makes sense to me, but the criteria for when this should apply could be difficult to determine.

Opt-in with a new DSL makes sense to me here.

What happens on uninstall?

[bevanjkay]

On uninstall we do run the quit and signal directives, but not on upgrade or reinstall.

[MikeMcQuaid]

@bevanjkay Gotcha. Could you dig up the PR that changed this, too?

[bevanjkay]

Here's the related PR: #16507

[MikeMcQuaid]

Thanks @bevanjkay. Yeh, I think a new DSL/parameter is warranted here.

[bevanjkay]

Can you think of an existing dsl that has a similar parameter I can use as a guide?

[MikeMcQuaid]

@bevanjkay depends_on I think is the best model here? It may be more complicated than you need, though. Feel free to hack something together and open a very early draft WIP PR and I'll help you from there 👍🏻