git annex webapp now opens a browser to the webapp

Also, starts the assistant if it wasn't already running.

Command/WebApp.hs

@@ -0,0 +1,58 @@
+{- git-annex webapp launcher
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Command.WebApp where
+
+import Common.Annex
+import Command
+import Assistant
+import Utility.WebApp
+import Utility.Daemon
+import qualified Annex
+
+import Control.Concurrent
+import System.Posix.Process
+
+def :: [Command]
+def = [command "webapp" paramNothing seek "launch webapp"]
+
+seek :: [CommandSeek]
+seek = [withNothing start]
+
+start :: CommandStart
+start = notBareRepo $ do
+	r <- checkpid
+	when (r == Nothing) $
+		startassistant
+	f <- liftIO . absPath =<< fromRepo gitAnnexHtmlShim
+	let url = "file://" ++ f
+	ifM (liftIO $ runBrowser url)
+		( stop
+		, error $ "failed to start web browser on url " ++ url
+		)
+	where
+		checkpid = do
+			pidfile <- fromRepo gitAnnexPidFile
+			liftIO $ checkDaemon pidfile
+		startassistant = do
+			{- Fork a separate process to run the assistant,
+			 - with a copy of the Annex state. -}
+			state <- Annex.getState id
+			liftIO $ void $ forkProcess $
+				Annex.eval state $ startDaemon True False
+			waitdaemon (100 :: Int)
+		waitdaemon 0 = error "failed to start git-annex assistant"
+		waitdaemon n = do
+			r <- checkpid
+			case r of
+				Just _ -> return ()
+				Nothing -> do
+					liftIO $
+						threadDelay 100000 -- 0.1 seconds
+					
+
+waitdaemon (n - 1)