plumb in LiveUpdate (WIP)

Each command that first checks preferred content (and/or required
content) and then does something that can change the sizes of
repositories needs to call prepareLiveUpdate, and plumb it through the
preferred content check and the location log update.

So far, only Command.Drop is done. Many other commands that don't need
to do this have been updated to keep working.

There may be some calls to NoLiveUpdate in places where that should be
done. All will need to be double checked.

Not currently in a compilable state.

Database/RepoSize.hs

@@ -6,7 +6,6 @@
  -}
 
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE QuasiQuotes, TypeFamilies, TemplateHaskell #-}
 {-# LANGUAGE OverloadedStrings, GADTs, FlexibleContexts #-}
 {-# LANGUAGE MultiParamTypeClasses, GeneralizedNewtypeDeriving #-}
@@ -21,6 +20,7 @@
 
 module Database.RepoSize (
 	RepoSizeHandle,
+	getRepoSizeHandle,
 	openDb,
 	closeDb,
 	getRepoSizes,
@@ -31,22 +31,20 @@ module Database.RepoSize (
 ) where
 
 import Annex.Common
-import Annex.LockFile
-import Types.RepoSize
-import Git.Types
+import qualified Annex
+import Database.RepoSize.Handle
 import qualified Database.Handle as H
 import Database.Init
 import Database.Utility
 import Database.Types
+import Annex.LockFile
+import Git.Types
 import qualified Utility.RawFilePath as R
 
 import Database.Persist.Sql hiding (Key)
 import Database.Persist.TH
 import qualified System.FilePath.ByteString as P
 import qualified Data.Map as M
-import qualified Data.Text as T
-
-newtype RepoSizeHandle = RepoSizeHandle (Maybe H.DbHandle)
 
 share [mkPersist sqlSettings, mkMigrate "migrateRepoSizes"] [persistLowerCase|
 -- Corresponds to location log information from the git-annex branch.
@@ -66,6 +64,15 @@ LiveSizeChanges
   UniqueLiveSizeChange repo key
 |]
 
+{- Gets a handle to the database. It's cached in Annex state. -}
+getRepoSizeHandle :: Annex RepoSizeHandle
+getRepoSizeHandle = Annex.getState Annex.reposizehandle >>= \case
+	Just h -> return h
+	Nothing -> do
+		h <- openDb
+		Annex.changeState $ \s -> s { Annex.reposizehandle = Just h }
+		return h
+
 {- Opens the database, creating it if it doesn't exist yet.
  -
  - Multiple readers and writers can have the database open at the same
@@ -155,23 +162,24 @@ recordAnnexBranchCommit branchcommitsha = do
 	deleteWhere ([] :: [Filter AnnexBranch])
 	void $ insertUniqueFast $ AnnexBranch $ toSSha branchcommitsha
 
-data SizeChange = AddingKey | RemovingKey
-
 {- If there is already a size change for the same UUID and Key, it is
  - overwritten with the new size change. -}
-startingLiveSizeChange :: UUID -> Key -> SizeChange -> SqlPersistM ()
-startingLiveSizeChange u k sc = 
-	void $ upsertBy
+startingLiveSizeChange :: RepoSizeHandle -> UUID -> Key -> SizeChange -> IO ()
+startingLiveSizeChange (RepoSizeHandle (Just h)) u k sc = 
+	H.commitDb h $ void $ upsertBy
 		(UniqueLiveSizeChange u k)
 		(LiveSizeChanges u k sc)
 		[LiveSizeChangesChange =. sc]
+startingLiveSizeChange (RepoSizeHandle Nothing) _ _ _ = noop
 
-finishedLiveSizeChange :: UUID -> Key -> SizeChange -> SqlPersistM ()
-finishedLiveSizeChange u k sc = deleteWhere 
-	[ LiveSizeChangesRepo ==. u
-	, LiveSizeChangesKey ==. k
-	, LiveSizeChangesChange ==. sc
-	]
+finishedLiveSizeChange :: RepoSizeHandle -> UUID -> Key -> SizeChange -> IO ()
+finishedLiveSizeChange (RepoSizeHandle (Just h)) u k sc = 
+	H.commitDb h $ deleteWhere 
+		[ LiveSizeChangesRepo ==. u
+		, LiveSizeChangesKey ==. k
+		, LiveSizeChangesChange ==. sc
+		]
+finishedLiveSizeChange (RepoSizeHandle Nothing) _ _ _ = noop
 
 getLiveSizeChanges :: RepoSizeHandle -> IO (M.Map UUID (Key, SizeChange))
 getLiveSizeChanges (RepoSizeHandle (Just h)) = H.queryDb h $ do
@@ -185,14 +193,3 @@ getLiveSizeChanges (RepoSizeHandle Nothing) = return mempty
 
 getLiveSizeChanges' :: SqlPersistM [Entity LiveSizeChanges]
 getLiveSizeChanges' = selectList [] []
-
-instance PersistField SizeChange where
-        toPersistValue AddingKey = toPersistValue (1 :: Int)
-	toPersistValue RemovingKey = toPersistValue (-1 :: Int)
-	fromPersistValue b = fromPersistValue b >>= \case
-		(1 :: Int) -> Right AddingKey
-		-1 -> Right RemovingKey
-		v -> Left $ T.pack $ "bad serialized SizeChange "++ show v
-
-instance PersistFieldSql SizeChange where
-        sqlType _ = SqlInt32