Add import and module support

[lspitzner]

#83 got closed due to me deleting the dev branch, so I now reopen it, including several finishing touches.

I am planning to merge this and make a new release with it in the next days. Again, sorry for the long hold-up, but fixing the low-level bug (see below) took a good bit of time and this caused me to put this off again and again.

In addition to what was last added to #83, this branch also contains the following changes:

• Merge in current master

• Fix bug in lower-level parts of brittany that led to discarding certain alternatives with the IEThingWith layouters. See af7f901, which is a one-liner fix, that nonetheless was rather time-consuming to diagnose.

• Prevent hanging indent for IEThingWith. This is a bugfix for the IndentPolicyLeft case and an opinionated improvement otherwise:

  -- hanging indent:
  import Test
    ( Long( List
          , Of
          , Things
          ) )
  -- fixed version:
  import Test
    ( Long
      ( List
      , Of
      , Things
      )
    )

• Retain empty lines before the module keyword that previously got eaten. Added a new BriDoc constructor just for this.

• Add config options _lconfig_reformatModulePreamble and _lconfig_allowSingleLineExportList (defaults True and False). The former can disable preamble formatting if desired. The latter is again the question of consistency - I like my exports in separate line even if it is just one short thingy. I was so arrogant to set the default according to my preference.

• Change _lconfig_importColumn default from 60 to 50, as was discussed in #83. I have left the test-config as-is (at 60) because I am lazy.

[tfausak]

🎉 Looks great!

cc @sniperrifle2004

[matthew-piziak]

Is anything blocking this PR?

[lspitzner]

Well there is this minor-feature request, which I implemented just now.

But that made me notice this:

#test long-module-name-hiding-items
import           TestJustShortEnoughModuleNameLike hiding ( abc
                                                          , def
                                                          , ghci
                                                          , jklm
                                                          )
import           TestJustAbitToLongModuleNameLikeTh
                                                   hiding ( abc
                                                          , def
                                                          , ghci
                                                          , jklm
                                                          )

currently gives

import           TestJustShortEnoughModuleNameLike hiding ( abc
                                                   , def
                                                   , ghci
                                                   , jklm
                                                   )
import           TestJustAbitToLongModuleNameLikeTh
                                                   hiding ( abc
                                                   , def
                                                   , ghci
                                                   , jklm
                                                   )

[lspitzner]

I'll merge anyway, this feature branch has lived long enough. Presuming the CI comes out green. There will be minor stuff to fix anyway in the future I guess.

[matthew-piziak]

🎉

[domenkozar]

🎉