Bring back old types of {hscolour,haddock}Pref and haddockForHackage.

[23Skidoo]

Fixes #4123.

[mention-bot]

@23Skidoo, thanks for your PR! By analyzing the history of the files in this pull request, we identified @bennofs, @dcoutts and @Saizan to be potential reviewers.

[23Skidoo]

@rthomas If people agree that this is an acceptable fix, we'll need a new Cabal lib release from the 1.24 branch.

[23Skidoo]

@dcoutts @hvr @ezyang @bennofs Any objections to this?

[23Skidoo]

This appears to be only a partial fix for #4123, since a0b4956 also contains the following change:

-    haddockForHackage   :: Flag Bool,
+    haddockForHackage   :: Flag HaddockTarget,

[hvr]

@23Skidoo we should also try comparing the API between 1.24.0.0 and 1.24.1 with something like https://hackage.haskell.org/package/hackage-diff to make sure there weren't other non-backward compat changes (at the type-level, at least) that snuck in

[23Skidoo]

Pushed an updated fix.

[23Skidoo]

@hvr I tried that, but the result was somewhat disappointing:

$ hackage-diff Cabal 1.24.0.0 1.24.1.0
Downloading / Reading Hoogle DBs...
Parsing Hoogle DBs...
endOfInput

Filed an issue (blitzcode/hackage-diff#6).

[23Skidoo]

All right, I'm merging this.

[23Skidoo]

@rthomas Ping.

[phadej]

@23Skidoo try hackage-diff --mode=builddb

[23Skidoo]

@phadej Here's the result:

$ hackage-diff --mode=builddb Cabal 1.24.0.0 1.24.1.0        
Downloading Cabal-1.24.0.0...
Downloading Cabal-1.24.1.0...
Processing Cabal-1.24.0.0...
  Creating Sandbox
  Installing Dependencies
  Configuring
  Building Haddock
Processing Cabal-1.24.1.0...
  Creating Sandbox
  Installing Dependencies
  Configuring
  Building Haddock

--- Diff for | 1.24.0.0 → 1.24.1.0 | ---

· Distribution.Compat.Binary
· Distribution.Compat.ReadP
· Distribution.Compat.Semigroup
· Distribution.PackageDescription.Utils
· Distribution.Simple.CCompiler
· Distribution.Simple.PreProcess.Unlit
· Distribution.Simple.Program.Internal
· Distribution.TestSuite

[+ Added] [- Removed] [× Modified] [· Unmodified]

Looks kinda strange to be honest. /cc @blitzcode

[bgamari]

@23Skidoo, when do you think we'll be able to get a new 1.24 release?

[23Skidoo]

@bgamari I'll do it today. @rthomas seems to be away or something.