Added command line parameter to set portable

If parameter included, home directory will be copied to the portable
location to make this a portable install

src/browser/atom-portable.coffee

@@ -5,7 +5,11 @@ module.exports =
 class AtomPortable
   @portableAtomHomePath: ->
     execDirectoryPath = path.dirname(process.execPath)
-    return path.join(execDirectoryPath, "../.atom")
+    return path.join(execDirectoryPath, "../.atom/")
+
+  @setPortable: (existingAtomHome) ->
+    fs.copySync(existingAtomHome, @portableAtomHomePath())
+
   @isPortableInstall: (platform, environmentAtomHome) ->
     return false unless platform is 'win32'
     return false if environmentAtomHome

src/browser/main.coffee

@@ -61,6 +61,7 @@ setupAtomHome = (args) ->
   return if process.env.ATOM_HOME
   atomHome = path.join(app.getHomeDir(), '.atom')
   AtomPortable = require './atom-portable'
+  AtomPortable.setPortable(atomHome) if not AtomPortable.isPortableInstall(process.platform, process.env.ATOM_HOME) and args.setPortable
   atomHome = AtomPortable.portableAtomHomePath() if AtomPortable.isPortableInstall process.platform, process.env.ATOM_HOME
   atomHome = fs.realpathSync(atomHome)
   fs.statSync(atomHome)
@@ -107,6 +108,7 @@ parseCommandLine = ->
   options.alias('t', 'test').boolean('t').describe('t', 'Run the specified specs and exit with error code on failures.')
   options.alias('v', 'version').boolean('v').describe('v', 'Print the version.')
   options.alias('w', 'wait').boolean('w').describe('w', 'Wait for window to be closed before returning.')
+  options.alias('p', 'set-portable').boolean('p').describe('p', 'Set portable mode.')
   options.string('socket-path')
 
   args = options.argv
@@ -132,6 +134,7 @@ parseCommandLine = ->
   profileStartup = args['profile-startup']
   urlsToOpen = []
   devResourcePath = process.env.ATOM_DEV_RESOURCE_PATH ? path.join(app.getHomeDir(), 'github', 'atom')
+  setPortable = args['set-portable']
 
   if args['resource-path']
     devMode = true
@@ -161,6 +164,6 @@ parseCommandLine = ->
 
   {resourcePath, devResourcePath, pathsToOpen, urlsToOpen, executedFrom, test,
    version, pidToKillWhenClosed, devMode, safeMode, newWindow, specDirectory,
-   logFile, socketPath, profileStartup}
+   logFile, socketPath, profileStartup, setPortable}
 
 start()