start splitting out readonly values from AnnexState

Values in AnnexRead can be read more efficiently, without MVar overhead.
Only a few things have been moved into there, and the performance
increase so far is not likely to be noticable.

This is groundwork for putting more stuff in there, particularly a value
that indicates if debugging is enabled.

The obvious next step is to change option parsing to not run in the
Annex monad to set values in AnnexState, and instead return a pure value
that gets stored in AnnexRead.

CmdLine/Action.hs

@@ -68,9 +68,10 @@ commandAction start = getConcurrency >>= \case
 		Just tv -> 
 			liftIO (atomically (waitStartWorkerSlot tv)) >>=
 				maybe runnonconcurrent (runconcurrent' tv)
-	runconcurrent' tv (workerst, workerstage) = do
-		aid <- liftIO $ async $ snd <$> Annex.run workerst
-			(concurrentjob workerst)
+	runconcurrent' tv (workerstrd, workerstage) = do
+		aid <- liftIO $ async $ snd 
+			<$> Annex.run workerstrd
+				(concurrentjob (fst workerstrd))
 		liftIO $ atomically $ do
 			pool <- takeTMVar tv
 			let !pool' = addWorkerPool (ActiveWorker aid workerstage) pool
@@ -78,12 +79,12 @@ commandAction start = getConcurrency >>= \case
 		void $ liftIO $ forkIO $ debugLocks $ do
 			-- accountCommandAction will usually catch
 			-- exceptions. Just in case, fall back to the
-			-- original workerst.
-			workerst' <- either (const workerst) id
+			-- original workerstrd.
+			workerstrd' <- either (const workerstrd) id
 				<$> waitCatch aid
 			atomically $ do
 				pool <- takeTMVar tv
-				let !pool' = deactivateWorker pool aid workerst'
+				let !pool' = deactivateWorker pool aid workerstrd'
 				putTMVar tv pool'
 	
 	concurrentjob workerst = start >>= \case
@@ -133,12 +134,12 @@ finishCommandActions = Annex.getState Annex.workers >>= \case
 	Nothing -> noop
 	Just tv -> do
 		Annex.changeState $ \s -> s { Annex.workers = Nothing }
-		sts <- liftIO $ atomically $ do
+		vs <- liftIO $ atomically $ do
 			pool <- readTMVar tv
 			if allIdle pool
 				then return (spareVals pool)
 				else retry
-		mapM_ mergeState sts
+		mapM_ (mergeState . fst) vs
 
 {- Waits for all worker threads that have been started so far to finish. -}
 waitForAllRunningCommandActions :: Annex ()
@@ -254,8 +255,9 @@ startConcurrency usedstages a = do
 		Annex.changeState $ \s -> s { Annex.workers = Just tv }
 		prepDupState
 		st <- dupState
+		rd <- Annex.getRead id
 		liftIO $ atomically $ putTMVar tv $
-			allocateWorkerPool st (max n 1) usedstages
+			allocateWorkerPool (st, rd) (max n 1) usedstages
 
 -- Make sure that some expensive actions have been done before
 -- starting threads. This way the state has them already run,
@@ -277,7 +279,7 @@ ensureOnlyActionOn k a = debugLocks $
 	go (Concurrent _) = goconcurrent
 	go ConcurrentPerCpu = goconcurrent
 	goconcurrent = do
-		tv <- Annex.getState Annex.activekeys
+		tv <- Annex.getRead Annex.activekeys
 		bracket (setup tv) id (const a)
 	setup tv = liftIO $ do
 		mytid <- myThreadId