Resolve #6369 and #6393: Allow cabal v2-install pkgname:exename or http://example.com/package.tar.gz(#sha256=abcde...)

[phadej]

No description provided.

[phadej]

Also added sha256 checking to fetchAndReadSourcePackageRemoteTarball.

Maybe that functionality should be in downloadURI itself, but this is good for now.

As a side-effect packages: https://... should work with sha256 functionality as well.

demo: incorrect hash

% cabal install 'https://hackage.haskell.org/package/cabal-fmt-0.1.2/cabal-fmt-0.1.2.tar.gz#sha256=21cdc5661958a703303d2'
Downloading
https://hackage.haskell.org/package/cabal-fmt-0.1.2/cabal-fmt-0.1.2.tar.gz
cabal: SHA256 doesn't match for
https://hackage.haskell.org/package/cabal-fmt-0.1.2/cabal-fmt-0.1.2.tar.gz
expected 21cdc5661958a703303d actual
aae556efbcaddfd65c6a1c1811b122b0d8c8d00624c8c2e36aabb5e9f9ea9840

demo: correct hash

% cabal install 'https://hackage.haskell.org/package/cabal-fmt-0.1.2/cabal-fmt-0.1.2.tar.gz#sha256=aae556efbcaddfd65c6a1c1811b122b0d8c8d00624c8c2e36aabb5e9f9ea9840'
Downloading
https://hackage.haskell.org/package/cabal-fmt-0.1.2/cabal-fmt-0.1.2.tar.gz
Resolving dependencies...
Build profile: -w ghc-8.6.5 -O1
In order, the following will be built (use -v for more details):
 - cabal-fmt-0.1.2 (lib:cabal-fmt-internal) (requires build)
 - cabal-fmt-0.1.2 (exe:cabal-fmt) (requires build)
Configuring library 'cabal-fmt-internal' for cabal-fmt-0.1.2..
Preprocessing library 'cabal-fmt-internal' for cabal-fmt-0.1.2..
Building library 'cabal-fmt-internal' for cabal-fmt-0.1.2..
[ 1 of 13] Compiling CabalFmt.Comments ( src/CabalFmt/Comments.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Comments.o )
[ 2 of 13] Compiling CabalFmt.Error   ( src/CabalFmt/Error.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Error.o )
[ 3 of 13] Compiling CabalFmt.Fields  ( src/CabalFmt/Fields.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Fields.o )
[ 4 of 13] Compiling CabalFmt.Fields.Extensions ( src/CabalFmt/Fields/Extensions.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Fields/Extensions.o )
[ 5 of 13] Compiling CabalFmt.Fields.Modules ( src/CabalFmt/Fields/Modules.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Fields/Modules.o )
[ 6 of 13] Compiling CabalFmt.Options ( src/CabalFmt/Options.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Options.o )
[ 7 of 13] Compiling CabalFmt.Monad   ( src/CabalFmt/Monad.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Monad.o )
[ 8 of 13] Compiling CabalFmt.Fields.TestedWith ( src/CabalFmt/Fields/TestedWith.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Fields/TestedWith.o )
[ 9 of 13] Compiling CabalFmt.Fields.BuildDepends ( src/CabalFmt/Fields/BuildDepends.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Fields/BuildDepends.o )
[10 of 13] Compiling CabalFmt.Parser  ( src/CabalFmt/Parser.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Parser.o )
[11 of 13] Compiling CabalFmt.Pragma  ( src/CabalFmt/Pragma.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Pragma.o )
[12 of 13] Compiling CabalFmt.Refactoring ( src/CabalFmt/Refactoring.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt/Refactoring.o )
[13 of 13] Compiling CabalFmt         ( src/CabalFmt.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/l/cabal-fmt-internal/build/cabal-fmt-internal/CabalFmt.o )
Configuring executable 'cabal-fmt' for cabal-fmt-0.1.2..
Preprocessing executable 'cabal-fmt' for cabal-fmt-0.1.2..
Building executable 'cabal-fmt' for cabal-fmt-0.1.2..
[1 of 2] Compiling Paths_cabal_fmt  ( /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/x/cabal-fmt/build/cabal-fmt/autogen/Paths_cabal_fmt.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/x/cabal-fmt/build/cabal-fmt/cabal-fmt-tmp/Paths_cabal_fmt.o )
[2 of 2] Compiling Main             ( cli/Main.hs, /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/x/cabal-fmt/build/cabal-fmt/cabal-fmt-tmp/Main.o )
Linking /tmp/cabal-install.-130794/dist-newstyle/build/x86_64-linux/ghc-8.6.5/cabal-fmt-0.1.2/x/cabal-fmt/build/cabal-fmt/cabal-fmt ...
Symlinking 'cabal-fmt'