Duncan Coutts authored Jan 05, 2016 and Ben Gamari committed Jan 05, 2016

A set of changes to enable local ghc env files to be useful for tools
like cabal. Ultimately it will allow cabal to maintain a ghc env file so
that users can simple run ghc or ghci in a project directory and get the
expected environment of the project.

Change the name of .ghc.environment files to include the platform and
ghc version, e.g. .ghc.environment.x86_64-linux-7.6.3, since their
content is version specific. Strictly speaking this is not backwards
compatible, but we think this feature is not widely used yet.

"Look up" for a local env file, like the behaviour of git/darcs etc. So
you can be anywhere within a project and get the expected environment.

Don't look for local env files when -hide-all-packages is given.

Extend the syntax of env files to allow specifying package dbs too.

Test Plan:
Currently completely untested. Compiles, that is all.
Sorry, have to disappear for the hols.

Reviewers: hvr, ezyang, austin, bgamari

Reviewed By: ezyang, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1668

GHC Trac Issues: #11268