annex.thin

Decided it's too scary to make v6 unlocked files have 1 copy by default,
but that should be available to those who need it. This is consistent with
git-annex not dropping unused content without --force, etc.

* Added annex.thin setting, which makes unlocked files in v6 repositories
  be hard linked to their content, instead of a copy. This saves disk
  space but means any modification of an unlocked file will lose the local
  (and possibly only) copy of the old version.
* Enable annex.thin by default on upgrade from direct mode to v6, since
  direct mode made the same tradeoff.
* fix: Adjusts unlocked files as configured by annex.thin.

Upgrade/V5.hs

@@ -8,18 +8,20 @@
 module Upgrade.V5 where
 
 import Common.Annex
+import qualified Annex
 import Config
 import Annex.InodeSentinal
 import Annex.Link
 import Annex.Direct
 import Annex.Content
-import Annex.WorkTree
+import Annex.CatFile
 import qualified Database.Keys
 import qualified Annex.Content.Direct as Direct
 import qualified Git
 import qualified Git.LsFiles
 import qualified Git.Branch
 import Git.FileMode
+import Git.Config
 import Utility.InodeCache
 
 upgrade :: Bool -> Annex Bool
@@ -27,6 +29,11 @@ upgrade automatic = do
 	unless automatic $
 		showAction "v5 to v6"
 	whenM isDirect $ do
+		{- Direct mode makes the same tradeoff of using less disk
+		 - space, with less preservation of old versions of files
+		 - as does annex.thin. -}
+		setConfig (annexConfig "thin") (boolConfig True)
+		Annex.changeGitConfig $ \c -> c { annexThin = True }
 		{- Since upgrade from direct mode changes how files
 		 - are represented in git, commit any changes in the
 		 - work tree first. -}
@@ -70,7 +77,9 @@ upgradeDirectWorkTree = do
 	void $ liftIO clean
   where
 	go (f, Just _sha, Just mode) | isSymLink mode = do
-		mk <- lookupFile f
+		-- Cannot use lookupFile here, as we're in between direct
+		-- mode and v6.
+		mk <- catKeyFile f
 		case mk of
 			Nothing -> noop
 			Just k -> do
@@ -84,13 +93,13 @@ upgradeDirectWorkTree = do
 	go _ = noop
 
 	fromdirect f k = do
-		-- If linkAnnex fails for some reason, the work tree file
+		-- If linkToAnnex fails for some reason, the work tree file
 		-- still has the content; the annex object file is just
 		-- not populated with it. Since the work tree file
 		-- is recorded as an associated file, things will still
 		-- work that way, it's just not ideal.
 		ic <- withTSDelta (liftIO . genInodeCache f)
-		void $ linkAnnex k f ic
+		void $ linkToAnnex k f ic
 	writepointer f k = liftIO $ do
 		nukeFile f
 		writeFile f (formatPointer k)