atomic file retrieval from backends

Commands.hs

@@ -156,13 +156,16 @@ getCmd file = notinBackend file err $ \(key, backend) -> do
 			showStart "get" file
 			g <- Annex.gitRepo
 			let dest = annexLocation g key
-			liftIO $ createDirectoryIfMissing True (parentDir dest)
-			success <- Backend.retrieveKeyFile backend key dest
+			let tmp = (annexTmpLocation g) ++ (keyFile key)
+			liftIO $ createDirectoryIfMissing True (parentDir tmp)
+			success <- Backend.retrieveKeyFile backend key tmp
 			if (success)
 				then do
+					liftIO $ renameFile tmp dest	
 					logStatus key ValuePresent
 					showEndOk
-				else showEndFail "get" file
+				else do
+					showEndFail "get" file
 	where
 		err = error $ "not annexed " ++ file
 

Core.hs

@@ -29,6 +29,8 @@ startup flags = do
 shutdown :: Annex ()
 shutdown = do
 	g <- Annex.gitRepo
+
+	-- handle pending commits
 	nocommit <- Annex.flagIsSet NoCommit
 	needcommit <- Annex.flagIsSet NeedCommit
 	if (needcommit && not nocommit)
@@ -36,6 +38,13 @@ shutdown = do
 			"git-annex log update", gitStateDir g]
 		else return ()
 
+	-- clean up any files left in the temp directory
+	let tmp = annexTmpLocation g
+	exists <- liftIO $ doesDirectoryExist tmp
+	if (exists)
+		then liftIO $ removeDirectoryRecursive $ tmp
+		else return ()
+
 {- configure git to use union merge driver on state files, if it is not
  - already -}
 gitAttributes :: Git.Repo -> IO ()

Locations.hs

@@ -7,7 +7,8 @@ module Locations (
 	keyFile,
 	fileKey,
 	annexLocation,
-	annexLocationRelative
+	annexLocationRelative,
+	annexTmpLocation
 ) where
 
 import Data.String.Utils
@@ -36,6 +37,11 @@ annexLocation r key =
 annexLocationRelative :: Git.Repo -> Key -> FilePath
 annexLocationRelative r key = Git.dir r ++ "/annex/" ++ (keyFile key)
 
+{- .git-annex/tmp is used for temp files
+ -}
+annexTmpLocation :: Git.Repo -> FilePath
+annexTmpLocation r = (Git.workTree r) ++ "/" ++ Git.dir r ++ "/annex/tmp/"
+
 {- Converts a key into a filename fragment.
  -
  - Escape "/" in the key name, to keep a flat tree of files and avoid

TODO

@@ -1,9 +1,6 @@
 * bug: cannot "git annex ../foo"   (GitRepo.relative is buggy and
   git-ls-files also refuses w/o --full-name, which would need other changes)
 
-* bug: git annex add file  is silent if file was a symlink and got replaced
-  with a file. The you then git command -a, you'll check in the fil contents..
-
 * --push/--pull should take a reponame and files, and push those files
   to that repo; dropping them from the current repo
 
@@ -17,9 +14,6 @@
 * Support for remote git repositories (ssh:// specifically can be made to
   work, although the other end probably needs to have git-annex installed..)
 
-* Copy files atomically, don't leave a partial key on interrupt.
-  (Fix for URL download too..)
-
 * Find a way to copy a file with a progress bar, while still preserving 
   stat. Easiest way might be to use pv and fix up the permissions etc
   after?