Add stack path --programs-path option

ChangeLog.md

@@ -13,8 +13,9 @@ Behavior changes:
 * `stack init` now ignores symlinks when searching for cabal files. It also now
   ignores any directory that begins with `.` (as well as `dist` dirs) - before
   it would only ignore `.git`, `.stack-work`, and `dist`.
-* `stack path --ghc-paths` is replaced with `--compiler-path` which points
-  directly at the binary used in the current project.
+* The `stack path --ghc-paths` option is renamed to `--programs-path`.
+  `--compiler-path` is added, which points directly at the compiler used in
+  the current project.
 
 Other enhancements:
 

doc/GUIDE.md

@@ -1473,6 +1473,7 @@ global-stack-root: /home/michael/.stack
 project-root: /home/michael/wai
 config-location: /home/michael/wai/stack.yaml
 bin-path: /home/michael/.stack/snapshots/x86_64-linux/lts-2.17/7.8.4/bin:/home/michael/.stack/programs/x86_64-linux/ghc-7.8.4/bin:/home/michael/.stack/programs/x86_64-linux/ghc-7.10.2/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+programs-path: /home/michael/.stack/programs/x86_64-linux
 compiler-path: /home/michael/.stack/programs/x86_64-linux/ghc-7.8.4/bin/ghc
 local-bin-path: /home/michael/.local/bin
 extra-include-dirs:
@@ -1487,21 +1488,24 @@ dist-dir: .stack-work/dist/x86_64-linux/Cabal-1.18.1.5
 ```
 
 In addition, `stack path` accepts command line arguments to state which of
-these keys you're interested in, which can be convenient for scripting. As an
-example, let's just get the path to the version of GHC we're using.
+these keys you're interested in, which can be convenient for scripting. As a
+simple example, let's find out which versions of GHC are installed locally:
 
 ```
-michael@d30748af6d3d:~/wai$ stack path --compiler-path
-/home/michael/.stack/programs/x86_64-linux/ghc-7.8.4/bin/ghc
+michael@d30748af6d3d:~/wai$ ls $(stack path --programs-path)/*.installed
+/home/michael/.stack/programs/x86_64-linux/ghc-7.10.2.installed
+/home/michael/.stack/programs/x86_64-linux/ghc-7.8.4.installed
 ```
 
+(Yes, that command requires a \*nix shell, and likely won't run on Windows.)
+
 While we're talking about paths, to wipe our stack install completely, here's
 what needs to be removed:
 
 1. The stack executable itself
 2. The stack root, e.g. `$HOME/.stack` on non-Windows systems.
     * See `stack path --global-stack-root`
-    * On Windows, you will also need to delete `stack path --ghc-paths`
+    * On Windows, you will also need to delete `stack path --programs-paths`
 3. Any local `.stack-work` directories inside a project
 
 ## exec

src/main/Main.hs

@@ -603,6 +603,9 @@ paths =
     , ( "PATH environment variable"
       , "bin-path"
       , T.pack . intercalate [searchPathSeparator] . eoPath . piEnvOverride )
+    , ( "Install location for GHC and other core tools"
+      , "programs-path"
+      , T.pack . toFilePathNoTrailingSep . configLocalPrograms . bcConfig . piBuildConfig )
     , ( "Compiler (e.g. ghc)"
       , "compiler-path"
       , T.pack . toFilePath . piCompilerPath )