Default-generated config is a bit of a mess

[23Skidoo]

User config file generated by default is a bit of a mess rn:

$ cabal --config=cabal-config user-config init
$ cat cabal-config

E.g. there's both a compiler and a with-compiler field, write-ghc-environment-files lacks a default, there are things like exact-configuration that should be hidden, etc. Looks like this started when new-install landed.

We should also think about putting more stuff into separate sections.

[phadej]

If nobody takes ownership (i.e. assigns to themselves) before Thursday 2019-12-05, I'll move this issue to 3.4 milestone.

[phadej]

Remilestoning for 3.4

[mmhat]

I just ran into this when I tried to set the build-info field included in the default config to some value. This does not work and judging from a quick look at the code it does not accept any value.