Update ghcjs.md based on changes in 0.1.8

Author: mgsloan

doc/ghcjs.md

@@ -0,0 +1,80 @@
+# GHCJS
+
+To use GHCJS with stack `>= 0.1.8`, place a GHCJS version in the [`compiler`](https://github.com/commercialhaskell/stack/blob/master/doc/yaml_configuration.md#compiler) field of `stack.yaml`.  After this, all stack commands should work with GHCJS, except for `ide`.  In particular:
+
+* `stack setup` will install GHCJS from source and boot it, which takes a long time.
+* `stack build` will compile your code to JavaScript.  In particular, the generated code for an executable ends up in `$(stack path --local-install-root)/bin/EXECUTABLE.jsexe/all.js` (bash syntax, where `EXECUTABLE` is the name of your executable).
+
+You can also build existing stack projects which target GHC, and instead build them with GHCJS.  For example: `stack build --compiler ghcjs-0.1.0.20150924_ghc-7.10.2`
+
+## Example Configurations
+
+### GHCJS (old base)
+
+You can use this resolver for GHCJS (old base) in your `stack.yaml`:
+
+```yaml
+compiler: ghcjs-0.1.0.20150924_ghc-7.10.2
+compiler-check: match-exact
+```
+
+### GHCJS `master` (a.k.a. improved base)
+
+To use the master branch, a.k.a improved base, add the following to your `stack.yaml`:
+
+```yaml
+compiler: ghcjs-0.2.0.20151001_ghc-7.10.2
+compiler-check: match-exact
+setup-info:
+  ghcjs:
+    source:
+      ghcjs-0.2.0.20151001_ghc-7.10.2:
+        url: "https://github.com/fizruk/ghcjs/releases/download/v0.2.0.20151001/ghcjs-0.2.0.20151001.tar.gz"
+```
+
+or for the 2015-10-29 master branch 
+```yaml
+compiler: ghcjs-0.2.0.20151029_ghc-7.10.2
+compiler-check: match-exact
+setup-info:
+  ghcjs:
+      source:
+            ghcjs-0.2.0.20151029_ghc-7.10.2:
+                    url: "https://github.com/nrolland/ghcjs/releases/download/v0.2.0.20151029/ghcjs-0.2.0.20151029.tar.gz"
+```
+
+### Custom installed GHCJS (development branch)
+
+In order to use a GHCJS installed on your path, just add the following to your `stack.yaml`:
+
+```yaml
+compiler: ghcjs-0.2.0_ghc-7.10.2
+```
+
+(Or, `ghcjs-0.1.0_ghc-7.10.2` if you are working with an older version)
+
+## Project with both client and server
+
+For projects with both a server and client, the recommended project organization is to put one or both of your `stack.yaml` files in sub-directories.  This way, you can use the current working directory to specify whether you're working on the client or server.  This will also allow more straightforward editor tooling, once projects like `ghc-mod` and `haskell-ide-engine` support GHCJS.
+
+For example, here's what a script for building both client and server looks like:
+
+```bash
+#!/bin/bash
+
+# Build the client
+stack build --stack-yaml=client/stack.yaml
+
+# Copy over the javascript
+rm -f server/static/all.js
+cp $(stack path --stack-yaml=client/stack.yaml --local-install-root)/bin/client.jsexe/all.js server/static/all.js
+
+# Build the server
+stack build --stack-yaml=server/stack.yaml
+```
+
+You can also put both the yaml files in the same directory, and have e.g. `ghcjs-stack.yaml`, but this won't work well with editor integrations.
+
+## Using stack without a snapshot
+
+If you don't want to use a snapshot, instead place the ghcjs version in the `resolver` field of your `stack.yaml`.  This is also necessary when using stack `< 0.1.8`.