Take config from SHARELATEX_CONFIG env variable

libraries/settings/README.md

@@ -0,0 +1,19 @@
+settings-sharelatex
+===================
+
+A small module to allow global config settings to be set for all services
+within the ShareLaTeX architecture.
+
+Settings file location
+----------------------
+
+You can specify a custom location for the settings file by setting the
+`SHARELATEX_CONFIG` environment variable. E.g.
+
+	$ export SHARELATEX_CONFIG=/home/james/config/settings.development.coffee
+
+Otherwise, the settings will be loaded from `config/settings.NODE_ENV.coffee`,
+where `NODE_ENV` is another evnironment variable, or defaults to `development`.
+
+The config directory is first looked for in the current directory, and then relative
+to the settings module directory.

libraries/settings/Settings.coffee

@@ -2,10 +2,13 @@ fs = require "fs"
 path = require "path"
 env = (process.env.NODE_ENV or "development").toLowerCase()
 
-possibleConfigFiles = [
+if process.env.SHARELATEX_CONFIG?
+	possibleConfigFiles = [process.env.SHARELATEX_CONFIG]
+else
+	possibleConfigFiles = [
 		process.cwd() + "/config/settings.#{env}.coffee"
 		path.normalize(__dirname + "/../../config/settings.#{env}.coffee")
-]
+	]
 
 for file in possibleConfigFiles
 	if fs.existsSync(file)