cabal init -i: add the GHC2021 language option

* cabal init -i should autodetect author name and maintainer email (fix #8255)

Name and email are fetched from git config in the non-interactive init
already, and we plug that utility into the interactive one in this commit.

Testing becomes clunkier: the list of inputs have to hold an additional
string that will be used as the return value of
`Interactive.readProcessWithExitCode`, and here is why. Recall that this
method is used to call `git config` to perform autodetection. In the
real scenario (the `IO` instance of `Interactive`), it actually calls
out to `git`. In the testing scenario (the `PurePrompt` instance of
`Interactive`), the method simply returns the next element of the list
of pre-defined inputs. So, the list of inputs to every relevant test has
to be adjusted.

* Add test checking that username/email can be autodetected

Build release archives (and validate) with GHC 9.2.3

cabal haddock imply enable-documentation

With this option, 'cabal get' writes to the destination directory only the
package description already available locally in one of the repository
indices.

The basename of the file name written to inside the target directory is
the package-id rather than only the package name.

This is mostly based on #1977

Co-authored-by: Miëtek Bak <mietek@bak.io>
Co-authored-by: Artem Pelenitsyn <a.pelenitsyn@gmail.com>

Co-authored-by: Herbert Valerio Riedel <hvr@gnu.org>
Co-authored-by: Miëtek Bak <mietek@bak.io>

* Print a warning when assertions are enabled.

Fixes #4377.

* Remove redundant imports

* Add changelog about

Co-authored-by: Mikhail Glushenkov <mikhail.glushenkov@gmail.com>

* (cabal check) Add “Unknown OS” test

* (cabal check) Add “Unknown arch” test

* (cabal check) Add “Unknown compiler” test

* (cabal check) Add “Package versions” check

* (cabal check) Add “`-Werror`” test

* (cabal check) Add “-j[n]” test

* (cabal check) Add “Defer type errors” test

* (cabal check) Add “Debug flag” test

* (cabal check) Add “Profiling flag” test

* (cabal check) Add “Unused flag” test

* (cabal check) Add “Custom fields” check

* (cabal check) Add “Paths_module extension” test

* (cabal check) Add “Setup bounds” test

* (cabal check) Add “Duplicate module” test

* (cabal check) Add “No license” check

* (cabal check) Add “NONE license” test

* (cabal check) Add AllRightsReserved warning test

* (cabal check) Add “compatibility” license test

With cabal-version < 1.4, some license (e.g. ISC) mess up the
parser.

* (cabal check) Add “Unknown license” test

* (cabal check) Add “Suspicious BSD4” test

* (cabal check) Add “Suspicious version” test

* (cabal check) Add “`license-file` missing” test

* (cabal check) Add “Unrecognised repo type” test

* (cabal check) Add “No `type`” test

* (cabal test) Add “No `location`” test

* (cabal check) Add “No `module`” test

Only for CVS repos.

* (cabal check) Add “`tag` needed” test

For `this`-type source-repositories.

* (cabal check) Add “Relative path” test

* (cabal check) Add “Good relative path” test

* (cabal check) Add “ghc-options” test.

Checks if there is a tricky GHC option in `ghc-options`. We will
*not* write an integration test for each offending option, just
one (in this case for `-fasm`) to make sure the field is scanned.

* (cabal check) Add “ghc-shared-options” test.

Checks if there is a tricky GHC option in `ghc-shared-options`. We
will *not* write an integration test for each offending option, just
one (in this case for `-fglasgow-exts`) to make sure the field is
scanned.

* (cabal check) Add “ghc-prof-options” test.

Checks if there is a tricky GHC option in `ghc-prof-options`. We
will *not* write an integration test for each offending option,
just one (in this case for `-o`) to make sure the field is scanned.

* (cabal check) Add “`cc-options` include” test

* (cabal check) Add “Cxx `extra-libraries`” test

* (cabal check) Add “`cc-options` libdir” test

* (cabal check) Add `Cxx -Os` test.

* (cabal check) Add “Portable CPP flags” test

* (cabal check) Add “Invalid on Win” test

* (cabal check) Add “Outside relative path” test

Note that this test is not atomic; it comes with a "not a good
relative path" error, and this is unavoidable.

* (cabal check) Add “Absolute path” test.

Note that this test is not atomic; comes with a "not a good relative
path" *and* a "does not match any file" warning. This is unfortunately
unavoidable.

* (cabal check) Add “points to dist/” test

* (cabal check) Add “Testsuite ≥1.8” test

* (cabal check) Add “Default language” test

* (cabal check) Add “Default language spec” test

* (cabal check) Add “Extra doc” test

* (cabal check) Add “Multilib/namedlib” test

* (cabal check) Add “Reexported module” test

* (cabal check) Add “Mixins” test

* (cabal check) Add “Extra framework dirs” test

* (cabal check) Add “Default extensions” test

* (cabal check) Add `extensions` test

* (cabal check) Add Sources test

* (cabal check) Add “Extra libs” test

* (cabal check) Add “Virtual modules” test

* (cabal check) Add “Source repository” test

* (cabal check) Add “Extension break” test

* (cabal check) Add “Custom setup” test

* (cabal check) Add “Autogen modules” test

* (cabal check) Add “No z-prefixed check” test

* (cabal check) Add “No `build-type` specified” test

* (cabal check) Add “Ignoring custom-setup” test

* (cabal check) Add “Unknown compiler” test

In `tested-with`

* (cabal check) Add “Unknown language” test

* (cabal check) Add “Unknown extension” test

* (cabal check) Add “Language as extension” test

Languages cannot be listed in `default-extensions`.

* (cabal check) Add “Deprecated extension” test

* (cabal check) Add “No synopsis” test

* (cabal check) Add “No description” test

* (cabal check) Add “No category” test

* (cabal check) Add “No maintainer” test

* (cabal check) Add “Short description” test

`description` should be longer than `synopsis`.

* (cabal check) Add “Invalid tested with range” test

* (cabal check) Add “Internal library” test

On impossible version ranges for internal libraries.

* (cabal check) Add BOM test

* (cabal check) Add “Name mismatch” test

* (cabal check) Add “Missing .cabal” test

* (cabal check) Add “Missing license file” test

* (cabal check) Add “No setup file” test

* (cabal check) Add “No configure file” test

* (cabal check) Add “Local paths” check

* (cabal check) Add “Missing VCS info” test

* (cabal check) Add “Partial extension match” test

* (cabal check) Add “Filename too long” check

Simplify -Werror warning

`cabal check` testuite: add sanity checks

All in `autogen-includes` hs to be in either `includes` or
`install-includes` (benchmark).

All in `autogen-modules` has to be present either in `other-modules`
or `exposed-modules` (benchmark).

`main-is` has to be one of: .hs, .lhs, C/C++/obj-C source file.
(benchmark)

All in `autogen-modules` has to be present either in `other-modules`
or `exposed-modules` (testsuite).

All in `autogen-includes` hs to be in either `includes` or
`install-includes` (testsuite).

You need `cabal-version` ≥ 1.18 to use C/C++/obj-C source files
in `main-is`. (testsuite)

`main-is` has to be one of: .hs, .lhs, C/C++/obj-C source file.
(testsuite)

All in `autogen-modules` has to be present either in `other-modules`
or `exposed-modules`.

All in `autogen-includes` hs to be in either `includes` or
`install-includes`.

You need `cabal-version` ≥ 1.18 to use C/C++/obj-C source files
in `main-is`.

`main-is` has to be one of: .hs, .lhs, C/C++/obj-C source file.

All in `autogen-includes` hs to be in either `includes` or
`install-includes`.

All in `autogen-modules` has to be present either in `other-modules`
or `exposed-modules`.

`signatures` field can be used only with `cabal-version` ≥ 2.0

Internal libraries cannot have the same name as the pacakge.

Executables can have the same name as the external library.

No body: No executables, libraries, tests, or benchmarks found.

* CONTRIBUTING: Describe project and milestone usage

* pr8083: address code reviews

Co-authored-by: Artem Pelenitsyn <a.pelenitsyn@gmail.com>

CI: GHC 9.2.1 -> 9.2.2