Add better support for Haskell stack compiler tools (#1851)

* Add better support for Haskell stack compiler tools

This commit adds support for `stack` as the executable of a tool. This
follows a pattern that has been implemented for `bundler`'s tool chain.

* Move hlint command to linter file
* Add vader test for stack exec handling
* Update ghc-mod to support stack execution

`ghc-mod` was previously broken into 2 linters.

1. ghc_mod
2. stack_ghc_mod

This additional linter is not necessary with proper support for
executable variables and `stack exec` handling.

* Support stack exec in hfmt
* Support stack in hdevtools

ale_linters/haskell/ghc_mod.vim

@@ -0,0 +1,19 @@
+" Author: wizzup <wizzup@gmail.com>
+" Description: ghc-mod for Haskell files
+
+call ale#Set('haskell_ghc_mod_executable', 'ghc-mod')
+
+function! ale_linters#haskell#ghc_mod#GetCommand (buffer) abort
+    let l:executable = ale#Var(a:buffer, 'haskell_ghc_mod_executable')
+
+    return ale#handlers#haskell_stack#EscapeExecutable(l:executable, 'ghc-mod')
+    \   . ' --map-file %s=%t check %s'
+endfunction
+
+call ale#linter#Define('haskell', {
+\   'name': 'ghc_mod',
+\   'aliases': ['ghc-mod'],
+\   'executable_callback': ale#VarFunc('haskell_ghc_mod_executable'),
+\   'command_callback': 'ale_linters#haskell#ghc_mod#GetCommand',
+\   'callback': 'ale#handlers#haskell#HandleGHCFormat',
+\})