Periodically flush git command queue, to avoid boating memory usage too much.

Since the queue is flushed in between subcommand actions being run,
there should be no issues with actions that expect to queue up some stuff
and have it run after they do other stuff. So I didn't have to audit for
such assumptions.

AnnexQueue.hs

@@ -0,0 +1,47 @@
+{- git-annex command queue
+ -
+ - Copyright 2011 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module AnnexQueue (
+	add,
+	flush,
+	flushWhenFull
+) where
+
+import Control.Monad.State (liftIO)
+import Control.Monad (when, unless)
+
+import Annex
+import Messages
+import qualified GitQueue
+import Utility
+
+{- Adds a git command to the queue, possibly running previously queued
+ - actions if enough have accumulated. -}
+add :: String -> [CommandParam] -> FilePath -> Annex ()
+add command params file = do
+	q <- getState repoqueue
+	store $ GitQueue.add q command params file
+
+{- Runs the queue if it is full. Should be called periodically. -}
+flushWhenFull :: Annex ()
+flushWhenFull = do
+	q <- getState repoqueue
+	when (GitQueue.full q) $ flush False
+
+{- Runs (and empties) the queue. -}
+flush :: Bool -> Annex ()
+flush silent = do
+	q <- getState repoqueue
+	unless (0 == GitQueue.size q) $ do
+		unless silent $
+			showSideAction "Recording state in git..."
+		g <- gitRepo
+		q' <- liftIO $ GitQueue.flush g q
+		store q'
+
+store :: GitQueue.Queue -> Annex ()
+store q = changeState $ \s -> s { repoqueue = q }