Addition of ‘--work-dir’ option to override working directory, #1178

[mrkkrp]

Here I've started to work on this. Currently I've added --work-dir option represented by globalWorkDir in GlobalOpts. Please correct me if this is a wrong place to put this option.

Now my plan is:

1. Store this option is Stack monadic environment (Config?), so functions that need to know stack working directory could query it. I think HasConfig env, MonadReader env can be used.
2. Instead of workDirRel constant, use that value from config, this will probably add HasConfig, MonadReader env or similar constraint to some functions that previously didn't need it.
3. Take care of ignoreDirs which specifies which directories shouldn't be searched for .cabal files. It currently lists ".stack-work". With this change it would need to construct the list more “dynamically”.

My questions:

1. Is GlobalOpts is the right place to add --work-dir option?
2. In case GlobalOpts is the right place, where is the best place to pass the value globalWorkDir from GlobalOpts to Config so the rest of Stack can query it?

Well, the rest seems to be pretty easy to do (at least for now).

[mgsloan]

Take care of ignoreDirs which specifies which directories shouldn't be searched for .cabal files. It currently lists ".stack-work". With this change it would need to construct the list more “dynamically”.

I don't think this is necessary.

1. Is GlobalOpts is the right place to add --work-dir option?
2. In case GlobalOpts is the right place, where is the best place to pass the value globalWorkDir from GlobalOpts to Config so the rest of Stack can query it?

How about adding it directly to Config / ConfigMonoid ? This'd mean that it'd also be a stack.yaml field, which could certainly have its uses (ensuring that different dist dirs are used for two different configs)

[mrkkrp]

Good, I'll take that direction.

[mrkkrp]

Seems to work! That was fun, please review.

[mgsloan]

LGTM, thanks!

[lukexi]

Hmm, I'm confused as to why this is restricted to child directories of the current directory. In my use-case I'd like to use ".." as the .stack-work directory for a set of uncoupled but related projects, but this is disallowed by parseRelDir since:
commercialhaskell/path@87a56a9

[mrkkrp]

@lukexi, See this discussion.