* Fill in the functionality for the `depends_on :macos` stub
* de-document `caveats` method `os_version_only`
* clean up some related docs re: version strings
* add `depends_on_test.rb`
* clarify some related `depends_on :formula` doc, tests, and code
* formatting in test Casks
* "Canonical App Name" becomes "Simplified App Name"
* devscript `cask_namer` renamed to `generate_cask_token`
* doc file `CASK_NAMING_REFERENCE.md` renamed to `cask_token_reference.md`
* DSL uses `"#{token}"` for interpolation instead of `"#{title}"`
* documentation text
* backend code (variables, method, class names)
* error message text
* tests
* code comments
* Cask comments
* emphasize `tags :name`
* doc: use "vendor" consistently instead of "developer"
* doc: many man page argument descriptions were incorrect
* incidental clarifications
Many backend variables similar to `cask_name` or `cask` have
been standardized to `cask_token`, `token`, etc, resolving a long-
standing ambiguity in which variables named `cask` might contain
a Cask instance or a string token.
In many places the docs could be shortened from "Cask name" to
simply "token", which is desirable because we use the term "Cask"
in too many contexts.
`caskroom_only` was never documented. Its original purpose was
obsoleted in #4865, and its use has been recently been reduced to
two Casks.
This PR
* continues the rationalization of naming by changing `caskroom_only`
to `stage_only`. "stage" is the verb for "make a copy under the
caskroom directory"
* documents `stage_only`
* adds tests for `stage_only`
* validates the argument to `stage_only`
* gives sensible output in `brew cask info` for `stage_only` Casks
* enforces that `stage_only` cannot coexist with any activatable
artifacts
`caskroom_only` is still supported for backward compatibility,
but should be removed before 0.50.0.
* `checklinks` is a very simple implementation useful only for development purposes
* it has no test coverage, only one line of documentation
* users regularly experiment with it and break it, especially
`brew cask checklinks` with no arguments, which tests all Tapped Casks
* part of DSL 1.0 review
* `destination_path` was always a bit vague (it refers to
Cask-specific, version-specific location under
`/opt/homebrew-cask/Caskroom`)
* here renamed `staged_path` to match upcoming command verb
`brew cask stage`
* rename also intended to reduce confusion when we implement
copying as a configurable alternative to symlinking
* transitional `destination_path` methods to remain while
Casks are converted (this was documented as a part of the
DSL, and used by 39 Casks in main repo)
* unrelated variables containing "stage" recast for clarity
