Supports indirect mode on encfs in paranoia mode, and other filesystems that do not support hard links, but do support symlinks and other POSIX filesystem features.

Command/Add.hs

@@ -80,20 +80,21 @@ start file = ifAnnexed file addpresent add
 
 {- The file that's being added is locked down before a key is generated,
  - to prevent it from being modified in between. It's hard linked into a
- - temporary location, and its writable bits are removed. It could still be
- - written to by a process that already has it open for writing.
+ - temporary location (to prevent it being replaced with another file),
+ - and its writable bits are removed. It could still be written to by a
+ - process that already has it open for writing.
+ -
+ - On a crippled filesystem, no lock down is done; the file can be modified
+ - at any time, and the no hard link is made.
+ -
+ - On a filesystem without hard links, but not otherwise crippled,
+ - no hard link is made, but the write bit is still removed.
  -
  - Lockdown can fail if a file gets deleted, and Nothing will be returned.
  -}
 lockDown :: FilePath -> Annex (Maybe KeySource)
 lockDown file = ifM (crippledFileSystem)
-	( liftIO $ catchMaybeIO $ do
-		cache <- genInodeCache file
-		return $ KeySource
-			{ keyFilename = file
-			, contentLocation = file
-			, inodeCache = cache
-			}
+	( liftIO $ catchMaybeIO nohardlink
 	, do
 		tmp <- fromRepo gitAnnexTmpDir
 		createAnnexDirectory tmp
@@ -102,14 +103,24 @@ lockDown file = ifM (crippledFileSystem)
 			(tmpfile, h) <- openTempFile tmp (takeFileName file)
 			hClose h
 			nukeFile tmpfile
-			createLink file tmpfile
-			cache <- genInodeCache tmpfile
-			return $ KeySource
-				{ keyFilename = file
-				, contentLocation = tmpfile
-				, inodeCache = cache
-				}
+			withhardlink tmpfile `catchIO` const nohardlink
 	)
+  where
+  	nohardlink = do
+		cache <- genInodeCache file
+		return $ KeySource
+			{ keyFilename = file
+			, contentLocation = file
+			, inodeCache = cache
+			}
+	withhardlink tmpfile = do
+		createLink file tmpfile
+		cache <- genInodeCache tmpfile
+		return $ KeySource
+			{ keyFilename = file
+			, contentLocation = tmpfile
+			, inodeCache = cache
+			}
 
 {- Ingests a locked down file into the annex.
  -

Command/ReKey.hs

@@ -7,8 +7,6 @@
 
 module Command.ReKey where
 
-import System.PosixCompat.Files
-
 import Common.Annex
 import Command
 import qualified Annex
@@ -17,7 +15,6 @@ import Annex.Content
 import qualified Command.Add
 import Logs.Web
 import Logs.Location
-import Config
 import Utility.CopyFile
 
 def :: [Command]
@@ -49,18 +46,14 @@ perform file oldkey newkey = do
 			return True
 	next $ cleanup file oldkey newkey
 
-{- Make a hard link to the old key content, to avoid wasting disk space. -}
+{- Make a hard link to the old key content (when supported),
+ - to avoid wasting disk space. -}
 linkKey :: Key -> Key -> Annex Bool
 linkKey oldkey newkey = getViaTmpUnchecked newkey $ \tmp -> do
 	src <- calcRepo $ gitAnnexLocation oldkey
-	ifM (liftIO $ doesFileExist tmp)
+	liftIO $ ifM (doesFileExist tmp)
 		( return True
-		, ifM crippledFileSystem
-			( liftIO $ copyFileExternal src tmp
-			, do
-				liftIO $ createLink src tmp
-				return True
-			)
+		, createLinkOrCopy src tmp
 		)
 
 cleanup :: FilePath -> Key -> Key -> CommandCleanup

Init.hs

@@ -140,8 +140,6 @@ probeCrippledFileSystem = do
 	probe f = catchBoolIO $ do
 		let f2 = f ++ "2"
 		nukeFile f2
-		createLink f f2
-		nukeFile f2
 		createSymbolicLink f f2
 		nukeFile f2
 		preventWrite f

Remote/Rsync.hs

@@ -264,7 +264,7 @@ rsyncRemote o callback params = do
  -
  - This would not be necessary if the hash directory structure used locally
  - was always the same as that used on the rsync remote. So if that's ever
- - unified, this gets nicer. Especially in the crippled filesystem case.
+ - unified, this gets nicer.
  - (When we have the right hash directory structure, we can just
  - pass --include=X --include=X/Y --include=X/Y/file --exclude=*)
  -}
@@ -272,20 +272,11 @@ rsyncSend :: RsyncOpts -> MeterUpdate -> Key -> Bool -> FilePath -> Annex Bool
 rsyncSend o callback k canrename src = withRsyncScratchDir $ \tmp -> do
 	let dest = tmp </> Prelude.head (keyPaths k)
 	liftIO $ createDirectoryIfMissing True $ parentDir dest
-	ok <- if canrename
+	ok <- liftIO $ if canrename
 		then do
-			liftIO $ renameFile src dest
+			renameFile src dest
 			return True
-		else ifM crippledFileSystem
-			( liftIO $ copyFileExternal src dest
-			, do
-#ifndef __WINDOWS__
-				liftIO $ createLink src dest
-				return True
-#else
-				liftIO $ copyFileExternal src dest
-#endif
-			)
+		else createLinkOrCopy src dest
 	ps <- sendParams
 	if ok
 		then rsyncRemote o (Just callback) $ ps ++

Utility/CopyFile.hs

@@ -1,11 +1,16 @@
-{- git-annex file copying
+{- file copying
  -
- - Copyright 2010,2012 Joey Hess <joey@kitenet.net>
+ - Copyright 2010-2013 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
-module Utility.CopyFile (copyFileExternal) where
+{-# LANGUAGE CPP #-}
+
+module Utility.CopyFile (
+	copyFileExternal,
+	createLinkOrCopy
+) where
 
 import Common
 import qualified Build.SysConfig as SysConfig
@@ -23,3 +28,17 @@ copyFileExternal src dest = do
 		, (SysConfig.cp_a, Param "-a")
 		, (SysConfig.cp_p && not SysConfig.cp_a, Param "-p")
 		]
+
+{- Create a hard link if the filesystem allows it, and fall back to copying
+ - the file. -}
+createLinkOrCopy :: FilePath -> FilePath -> IO Bool
+#ifndef __WINDOWS__
+createLinkOrCopy src dest = go `catchIO` const fallback
+  where
+  	go = do
+		createLink src dest
+		return True
+  	fallback = copyFileExternal src dest
+#else
+createLinkOrCopy = copyFileExternal
+#endif

debian/changelog

@@ -1,3 +1,11 @@
+git-annex (4.20130602) UNRELEASED; urgency=low
+
+  * Supports indirect mode on encfs in paranoia mode, and other
+    filesystems that do not support hard links, but do support
+    symlinks and other POSIX filesystem features.
+
+ -- Joey Hess <joeyh@debian.org>  Mon, 10 Jun 2013 12:52:44 -0400
+
 git-annex (4.20130601) unstable; urgency=medium
 
   * XMPP: Git push over xmpp made much more robust.