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This matches what is produced by PrettyField, so that when we switch over the
cabal file generation from manual formatting to PrettyField formatting we see
the true diffs and less field indent line noise.

cabal-install support is very WIP

This PR adds `--exact` flag to the cabal list command which
enables exact match on the package name while searching.

Also refactor ./Setup sdist to not do anything fancy.
Now `./Setup sdist` and `v2-sdist` should produce close(r)
to same tarballs.

Fixes #5813.

- Always ask for SPDX expression, we can "convert" them to old format
- No default license
- Add cabal-version: 3.0 to the list
- cabal-version is asked using CabalSpecVersion type
- seems to fix what #6619 tries to fix:

```
% /code/shared-haskell/cabal/dist-newstyle/build/x86_64-linux/ghc-8.8.3/cabal-install-3.3.0.0/x/cabal/build/cabal/cabal init -l 'FOO AND BAR'
Cannot parse license: FOO AND BAR
CallStack (from HasCallStack):
  error, called at ./Distribution/ReadE.hs:42:24 in Cabal-3.3.0.0-inplace:Distribution.ReadE
```

an error, but it doesn't loop.

- We had to add gpdScannedVersion to permit solver to report
  about too new packages in the index.
  https://github.com/haskell/cabal/issues/6652
- It's hard to track what happening with Setup interface selection in
  ProjectPlanning.
  https://github.com/haskell/cabal/issues/6651 would help to
  make sense of it.

Init.Command - Main cabal init logic that ties everything together.
Init.Defaults - Default values for items not specified in config or arguments
Init.FileCreators - All the createXyz functions which write files (LICENSE, Main.hs, etc.)
Init.Prompt - Utilities for prompting the user for selections
Init.Utils - Misc utilities shared across the above modules

This change updates the `cabal install` command to use the default install
directory for executables if one was not specified in either Cabal's config file
or on the command line with the --installdir flag.

Previously this would error out, now it warns that it used the default and
continues.

PR #6624, resolves #5973.

Also refactor it to use more of utilities, i.e. be consistent

See #6210 for more information.

Also add validate-8.10.1 make rule

Cabal version 2.4 is over 2 years old at this point and has numerous additions
compared to the current default 1.10.

When `build-type: Simple` the contents of Setup.hs MUST BE standard. It is only
in advanced cases where a custom setup file is needed.

Move few Arbitrary instances to more correct places,
add tests

- Writing a regex to parse dates is awful.
- Add ShortText conversions to PackageName and UnqualComponentName
- Add mkDependency, which maintains the invariant
- Remove VersionRangeParens - it's not preserved by parsec . pretty
  roundtrip
- Move moree instances into Cabal-quickcheck,
  use the package in cabal-install tests

Make it, LocalRepo, RemoteRepo, IndexState and Timestamp use
Pretty/Parsec instead of Text

Mostly adding `unRepoName` to error printing statements

We can write URIs with a fragment like

    https://hackage.haskell.org/package/cabal-fmt-0.1.2/cabal-fmt-0.1.2.tar.gz#sha256=aae556efbcaddfd65c6a1c1811b122b0d8c8d00624c8c2e36aabb5e9f9ea9840

and downloadURI will check the hash after download before continuing.
The hash check supersedes ETag

And make it pipe output to `man -l -`.

Only on non-Windows and non-macOS. The unit-ids become a bit longer:

Changes e.g.

    component cabal-fmt-0.1.2-ff4d3d1e89ec09722d5bccbf9724beeddb2bd9dcd99a200ff350860e49ecb0f2
        include cabal-fmt-0.1.2-3fc69567df6c17a860b37365e18b4b35f7d2e64ffdbab5d91cd775762ae888f1
    unit cabal-fmt-0.1.2-ff4d3d1e89ec09722d5bccbf9724beeddb2bd9dcd99a200ff350860e49ecb0f2
        include cabal-fmt-0.1.2-3fc69567df6c17a860b37365e18b4b35f7d2e64ffdbab5d91cd775762ae888f1

to

    component cabal-fmt-0.1.2-e-cabal-fmt-173382ac142508c938885649c3384b3512c441f46ff13c57cda2f345fe5f0859
        include cabal-fmt-0.1.2-l-cabal-fmt-internal-3fc69567df6c17a860b37365e18b4b35f7d2e64ffdbab5d91cd775762ae888f1
    unit cabal-fmt-0.1.2-e-cabal-fmt-173382ac142508c938885649c3384b3512c441f46ff13c57cda2f345fe5f0859
        include cabal-fmt-0.1.2-l-cabal-fmt-internal-3fc69567df6c17a860b37365e18b4b35f7d2e64ffdbab5d91cd775762ae888f1

i.e.

    cabal-fmt-0.1.2-....
    cabal-fmt-0.1.2-....

to

    cabal-fmt-0.1.2-e-cabal-fmt-...
    cabal-fmt-0.1.2-l-cabal-fmt-internal-...

This helps debugging, especially when public multilibs will become more
popular.

Resolves https://github.com/haskell/cabal/issues/6485