[Issue 18649] curl on Ubuntu 18.04 depends on libcurl4, .deb installer depends on libcurl3

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18649

Martin Nowak <code at dawg.eu> changed:

           What    |Removed                     |Added
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                 CC|                            |code at dawg.eu

--- Comment #7 from Martin Nowak <code at dawg.eu> ---
- The libcurl dependency should be demoted to recommended (installed by
default) or suggested, atm. it's still a dependency.

- It's confusing to see libcurl3 as dependency and libcurl4-openssl-dev as
suggestion.
 
https://github.com/dlang/installer/blob/47830a15d1a576b683c92b4bb4adc4a1d83a2b5d/linux/dmd_deb.sh#L347-L348
  Has anyone ever succeeded to install that with `-o
APT::Install-Suggests="true"` or `--install-suggests`?

- It's a pity that debian doesn't have a meta-package for libcurl, but I'd
research how other packages resolved this issue (libcurl-ocaml depends on
libcurl3-gnutls while libcurl-ocaml-dev depends on libcurl4-gnutls-dev).

- Use an alternative package name `libcurl4 | libcurl3` to support
installations without libcurl4 availability. Assuming that all OSes with
libcurl4 switch to that by default, otherwise you'd be back to the conflict.

So how about:
DEPENDS='libc6, libc6-dev, gcc, libgcc1, libstdc++6'
RECOMMENDS='libcurl4 | libcurl3'
SUGGESTS='libcurl4-openssl-dev, gcc-multilib'

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