git-annex/Command/Watch.hs
Joey Hess cbdaccd44a run event handlers all in the same Annex monad
Uses a MVar again, as there seems no other way to thread the state through
inotify events.

This is a rather unsatisfactory result. I had wanted to run them in
the same monad so that the git queue could be used to coleasce git commands
and speed things up. But, that led to fragility: If several files are
added, and one is removed before queue flush, git add will fail to add
any of them. So, the queue is still explicitly flushed after each add for
now.

TODO: Investigate using git add --ignore-errors. This would need to be done
in Command.Add. And, git add still exits nonzero with it, so would need
to avoid crashing on queue flush.
2012-06-04 21:21:52 -04:00

107 lines
2.9 KiB
Haskell

{- git-annex command
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# LANGUAGE BangPatterns #-}
module Command.Watch where
import Common.Annex
import Command
import Utility.Inotify
import Utility.ThreadLock
import qualified Annex
import qualified Annex.Queue
import qualified Command.Add as Add
import qualified Git.Command
import qualified Backend
import Annex.Content
import Control.Exception as E
import System.INotify
import Control.Concurrent.MVar
def :: [Command]
def = [command "watch" paramPaths seek "watch for changes"]
seek :: [CommandSeek]
seek = [withNothing start]
start :: CommandStart
start = notBareRepo $ do
showStart "watch" "."
showAction "scanning"
inRepo $ Git.Command.run "add" [Param "--update"]
state <- Annex.getState id
mvar <- liftIO $ newMVar state
next $ next $ liftIO $ withINotify $ \i -> do
let hook a = Just $ runAnnex mvar a
watchDir i "." (not . gitdir)
(hook onAdd) (hook onAddSymlink)
(hook onDel) (hook onDelDir)
putStrLn "(started)"
waitForTermination
return True
where
gitdir dir = takeFileName dir /= ".git"
{- Runs a handler, inside the Annex monad.
-
- Exceptions by the handlers are ignored, otherwise a whole watcher
- thread could be crashed.
-}
runAnnex :: MVar Annex.AnnexState -> (FilePath -> Annex a) -> FilePath -> IO ()
runAnnex mvar a f = do
startstate <- takeMVar mvar
r <- E.try (go startstate) :: IO (Either E.SomeException Annex.AnnexState)
case r of
Left e -> do
putStrLn (show e)
putMVar mvar startstate
Right !newstate ->
putMVar mvar newstate
where
go state = Annex.exec state $ a f
{- Adding a file is the same as git-annex add.
- The git queue is immediately flushed, so the file is added to git
- now, rather than later (when it may have been already moved or deleted!) -}
onAdd :: FilePath -> Annex ()
onAdd file = do
void $ doCommand $ do
showStart "add" file
next $ Add.perform file
Annex.Queue.flush
{- A symlink might be an arbitrary symlink, which is just added.
- Or, if it is a git-annex symlink, ensure it points to the content
- before adding it.
-}
onAddSymlink :: FilePath -> Annex ()
onAddSymlink file = go =<< Backend.lookupFile file
where
go Nothing = addlink
go (Just (key, _)) = do
link <- calcGitLink file key
ifM ((==) link <$> liftIO (readSymbolicLink file))
( addlink
, do
liftIO $ removeFile file
liftIO $ createSymbolicLink link file
addlink
)
addlink = inRepo $ Git.Command.run "add"
[Params "--force --", File file]
onDel :: FilePath -> Annex ()
onDel file = inRepo $ Git.Command.run "rm"
[Params "--quiet --cached --ignore-unmatch --", File file]
{- A directory has been deleted, or moved, so tell git to remove anything
- that was inside it from its cache. -}
onDelDir :: FilePath -> Annex ()
onDelDir dir = inRepo $ Git.Command.run "rm"
[Params "--quiet -r --cached --ignore-unmatch --", File dir]