Addresses https://github.com/haskell/cabal/pull/2500#commitcomment-10817840.

Addresses https://github.com/haskell/cabal/pull/2500#commitcomment-10455644.

Only set rpath on dynamic executables

not static ones. They make no sense there, increase startup time and
may violate some distributions policy on rpaths. This closes #2625.

Fix #2598. Omit empty CondTree branches

Document 'extensions' field replacements

Resolves #2401.

Fix sandbox delete-source error message typo

\a is considered as a bell character, which is omitted as a result

[ci skip]

[ci skip]

Don't recompile C files unless needed

Make the modular solver the default always, and deprecate the top-down solver

Add support for base shims to the modular solver

Introduce "setup dependencies"

[ci skip]

Provide cabal_macros in c2hs invocation.

This commit includes cabal_macros in c2hs call, so it will
be possible to use MIN_VERSION macros in chs files.

The existing code supports reading multiple preferred-versions files in
the 00-index.tar and merging them. However it doesn't do it quite right
when the same file is updated, it merged them instead of the later one
overriding the first.

This should make no difference right now because the 00-index.tar
typically only contains a single preferred-versions file, with no
updates.

Implement offline mode for the 'install' command.

Improve a number of ghc-options checks

Currently there are no checks that need to be specific to one of them.
Both sets of options get used in distributed packages.

And extend it to cover other similar variants. People often put it in to
help them profile *this* package, but it causes problems for profiling
other packages. The -fprof-auto-exported is arguably ok though.

The -threaded flag really makes no difference for libraries, it's a
link-time option only.

Improve the package description check for -Werror and similar flags so
that they are allowed so long as they're not enabled by default. We
check the conditions that they're guarded by to make sure they're always
false (given the default values of the manual flags). Also extend the
error messages to explain how to use these flags with conditionals.

[ci skip]

When in offline mode, 'cabal install' only installs packages from the local
tarball cache. Offline mode can be enabled with the '--offline' flag.

Fixes #2566.

Use PVP-compliant example when warning about missing base upper bound

Refs hackage-server#253.

Force cabal upload to always use digest auth and never basic auth