Remove support for .zip format source distributions

[hvr]

cabal sdist has had support for generating .zipped source distributions ever since it was added in ae0dee3

    --targz                Produce a '.tar.gz' format archive (default and required for uploading to hackage)
    --zip                  Produce a '.zip' format archive

The original implementation relied on invoking an external zip executable, whereas in the course of the new-sdist implementation this the Haskell library zip-archive was used (see 8fe7607) thereby gaining an additional dependency.

However, it's not clear to me if this feature is even relevant to anyone anymore; This feature is also rather asymmetric as there's only write support but not read support for .zip sdists. I'd argue it'd be more in line w/ the KISS principle to handle this by a simple tgz2zip utility than to bloat cabal with trivial convenience concerns which lead to feature creep.

If nobody needs/uses this feature it'd be effectively dead-code and we should eliminate it in the interest of reducing current and future maintenance costs of additional code-paths as well as an additional library dependency.

Concretely, I suggest to

1. remove the --zip feature (and associated codepaths) from sdist & v2-sdist,
2. drop the zip-archive dependency, and
3. (optionally) if there's actually demand, implement a native Haskell tar2zip or tgz2zip tool and host its package on Hackage to satisfy the needs of what I believe to be a very small minority target audience :-)

[23Skidoo]

+1. I can see how .zip makes sense for distributing Windows binaries (Windows Explorer supports it natively), but for source packages it makes more sense to have a single standard format.

[phadej]

👍

EDIT I thought zip-archive was used for source-repositories; having it for new-sdist doesn't seen relevant.

[dcoutts]

Agreed.

[emilypi]

Finished as of #5755