remove unused backend machinery

The only remaining vestiage of backends is different types of keys. These
are still called "backends", mostly to avoid needing to change user interface
and configuration. But everything to do with storing keys in different
backends was gone; instead different types of remotes are used.

In the refactoring, lots of code was moved out of odd corners like
Backend.File, to closer to where it's used, like Command.Drop and
Command.Fsck. Quite a lot of dead code was removed. Several data structures
became simpler, which may result in better runtime efficiency. There should
be no user-visible changes.

Command/Fsck.hs

@@ -9,10 +9,15 @@ module Command.Fsck where
 
 import Control.Monad (when)
 import Control.Monad.State (liftIO)
+import System.Directory
+import Data.List
+import System.Posix.Files
 
 import Command
-import qualified Backend
 import qualified Annex
+import qualified Remote
+import qualified Types.Backend
+import qualified Types.Key
 import UUID
 import Types
 import Messages
@@ -20,6 +25,9 @@ import Utility
 import Content
 import LocationLog
 import Locations
+import Trust
+import DataUnits
+import Config
 
 command :: [Command]
 command = [repoCommand "fsck" (paramOptional $ paramRepeating paramPath) seek
@@ -40,7 +48,7 @@ perform key file backend numcopies = do
 	-- the location log is checked first, so that if it has bad data
 	-- that gets corrected
 	locationlogok <- verifyLocationLog key file
-	backendok <- Backend.fsckKey backend key (Just file) numcopies
+	backendok <- fsckKey backend key (Just file) numcopies
 	if locationlogok && backendok
 		then next $ return True
 		else stop
@@ -80,3 +88,68 @@ verifyLocationLog key file = do
 		fix g u s = do
 			showNote "fixing location log"
 			logChange g key u s
+
+{- Checks a key for problems. -}
+fsckKey :: Backend Annex -> Key -> Maybe FilePath -> Maybe Int -> Annex Bool
+fsckKey backend key file numcopies = do
+	size_ok <- checkKeySize key
+	copies_ok <- checkKeyNumCopies key file numcopies
+	backend_ok <-(Types.Backend.fsckKey backend) key
+	return $ size_ok && copies_ok && backend_ok
+
+{- The size of the data for a key is checked against the size encoded in
+ - the key's metadata, if available. -}
+checkKeySize :: Key -> Annex Bool
+checkKeySize key = do
+	g <- Annex.gitRepo
+	let file = gitAnnexLocation g key
+	present <- liftIO $ doesFileExist file
+	case (present, Types.Key.keySize key) of
+		(_, Nothing) -> return True
+		(False, _) -> return True
+		(True, Just size) -> do
+			stat <- liftIO $ getFileStatus file
+			let size' = fromIntegral (fileSize stat)
+			if size == size'
+				then return True
+				else do
+					dest <- moveBad key
+					warning $ "Bad file size (" ++
+						compareSizes storageUnits True size size' ++ 
+						"); moved to " ++ dest
+					return False
+
+
+checkKeyNumCopies :: Key -> Maybe FilePath -> Maybe Int -> Annex Bool
+checkKeyNumCopies key file numcopies = do
+	needed <- getNumCopies numcopies
+	locations <- keyLocations key
+	untrusted <- trustGet UnTrusted
+	let untrustedlocations = intersect untrusted locations
+	let safelocations = filter (`notElem` untrusted) locations
+	let present = length safelocations
+	if present < needed
+		then do
+			ppuuids <- Remote.prettyPrintUUIDs untrustedlocations
+			warning $ missingNote (filename file key) present needed ppuuids
+			return False
+		else return True
+	where
+		filename Nothing k = show k
+		filename (Just f) _ = f
+
+missingNote :: String -> Int -> Int -> String -> String
+missingNote file 0 _ [] = 
+		"** No known copies exist of " ++ file
+missingNote file 0 _ untrusted =
+		"Only these untrusted locations may have copies of " ++ file ++
+		"\n" ++ untrusted ++
+		"Back it up to trusted locations with git-annex copy."
+missingNote file present needed [] =
+		"Only " ++ show present ++ " of " ++ show needed ++ 
+		" trustworthy copies exist of " ++ file ++
+		"\nBack it up with git-annex copy."
+missingNote file present needed untrusted = 
+		missingNote file present needed [] ++
+		"\nThe following untrusted locations may also have copies: " ++
+		"\n" ++ untrusted