Fixes #2309, #1889.

Fixes #2461.

Say 16 days, rather than 16.3 days. The precision is quite unnecessary.

Instead of the old http://hackage.haskell.org/packages/archive
we can just use http://hackage.haskell.org/ and avoid doing
an http redirect. The old one continues to work of course.

Put full package name and version in library names, fixes #2437.

Reconfigure when there is no cabal file, fix #1905

This reverts commit 7da2a8eb.

[ci skip]

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Added checks to see if files and directories exist

Auto-generate ChangeLog.md in cabal init

Treat -O2 in ghc-options as a cabal check "warning"

Cabal : Fix incomplete pattern matches.

cabal-install.cabal : Add missing test dependency.

Closes: https://github.com/haskell/cabal/issues/2447

Client.Init: add ChangeLog.md to extra-source-files if necessary. If there's already a ChangeLog-like file, it won't generate ChangeLog.md.