Command `act-as-setup` is not documented

[philderbeast]

What is wrong with the docs?
The command cabal act-as-setup is not documented.

Additional context

$ grep -R 'act-as-setup' ./**/*.rst

$ cabal act-as-setup --help
Run as-if this was a Setup.hs

Usage: cabal act-as-setup

Flags for act-as-setup:
 -h, --help                     Show this help text
 --build-type=BUILD-TYPE        Use the given build type.

[philderbeast]

Only [Simple|Configure|Make] are permitted as --build-type=BUILD-TYPE. We could say this in cabal act-as-setup --help. For the other build types, the error messages are not very clear.

cabal/cabal-install/src/Distribution/Client/Main.hs

Lines 1478 to 1491 in 80a8ddf

	-- | Used as an entry point when cabal-install needs to invoke itself
	-- as a setup script. This can happen e.g. when doing parallel builds.
	actAsSetupAction :: ActAsSetupFlags -> [String] -> Action
	actAsSetupAction actAsSetupFlags args _globalFlags =
	let bt = fromFlag (actAsSetupBuildType actAsSetupFlags)
	in case bt of
	Simple -> Simple.defaultMainArgs args
	Configure ->
	Simple.defaultMainWithSetupHooksArgs
	Simple.autoconfSetupHooks
	args
	Make -> Make.defaultMainArgs args
	Hooks -> error "actAsSetupAction Hooks"
	Custom -> error "actAsSetupAction Custom"

$ cabal act-as-setup --build-type=Custom configure
actAsSetupAction Custom

HasCallStack backtrace:
  error, called at src/Distribution/Client/Main.hs:1491:19 in
cabal-install-3.17.0.0-a74fb577cd754495896e4904ddab92a148d50d098d461d822264e7e1f3edb90a
:Distribution.Client.Main

$ cabal act-as-setup --build-type=Hooks configure
actAsSetupAction Hooks

HasCallStack backtrace:
  error, called at src/Distribution/Client/Main.hs:1490:18 in
cabal-install-3.17.0.0-a74fb577cd754495896e4904ddab92a148d50d098d461d822264e7e1f3edb90a
:Distribution.Client.Main

[geekosaur]

TBH I'm not sure it should be; it's something of an internal implementation detail.

[philderbeast]

We use it in our tests and mention it in the Cabal-3.16.0.0 release notes

cabal/cabal-testsuite/src/Test/Cabal/Prelude.hs

Line 225 in 80a8ddf

-- We test `cabal act-as-setup` when running cabal-tests.