refactor git-annex branch log filename code into central location

Having one module that knows about all the filenames used on the branch
allows working back from an arbitrary filename to enough information about
it to implement dropping dead remotes and doing other log file compacting
as part of a forget transition.

Logs/Web.hs

@@ -11,8 +11,6 @@ module Logs.Web (
 	getUrls,
 	setUrlPresent,
 	setUrlMissing,
-	urlLog,
-	urlLogKey,
 	knownUrls,
 	Downloader(..),
 	getDownloader,
@@ -22,9 +20,9 @@ module Logs.Web (
 import qualified Data.ByteString.Lazy.Char8 as L
 
 import Common.Annex
+import Logs
 import Logs.Presence
 import Logs.Location
-import Types.Key
 import qualified Annex.Branch
 import Annex.CatFile
 import qualified Git
@@ -36,35 +34,9 @@ type URLString = String
 webUUID :: UUID
 webUUID = UUID "00000000-0000-0000-0000-000000000001"
 
-urlLogExt :: String
-urlLogExt = ".log.web"
-
-urlLog :: Key -> FilePath
-urlLog key = hashDirLower key </> keyFile key ++ urlLogExt
-
-{- Converts a url log file into a key.
- - (Does not work on oldurlLogs.) -}
-urlLogKey :: FilePath -> Maybe Key
-urlLogKey file
-	| ext == urlLogExt = fileKey base
-	| otherwise = Nothing
-  where
-  	(base, ext) = splitAt (length file - extlen) file
-	extlen = length urlLogExt
-
-isUrlLog :: FilePath -> Bool
-isUrlLog file = urlLogExt `isSuffixOf` file
-
-{- Used to store the urls elsewhere. -}
-oldurlLogs :: Key -> [FilePath]
-oldurlLogs key = 
-	[ "remote/web" </> hashDirLower key </> key2file key ++ ".log"
-	, "remote/web" </> hashDirLower key </> keyFile key ++ ".log"
-	]
-
 {- Gets all urls that a key might be available from. -}
 getUrls :: Key -> Annex [URLString]
-getUrls key = go $ urlLog key : oldurlLogs key
+getUrls key = go $ urlLogFile key : oldurlLogs key
   where
 	go [] = return []
 	go (l:ls) = do
@@ -77,13 +49,13 @@ setUrlPresent :: Key -> URLString -> Annex ()
 setUrlPresent key url = do
 	us <- getUrls key
 	unless (url `elem` us) $ do
-		addLog (urlLog key) =<< logNow InfoPresent url
+		addLog (urlLogFile key) =<< logNow InfoPresent url
 		-- update location log to indicate that the web has the key
 		logChange key webUUID InfoPresent
 
 setUrlMissing :: Key -> URLString -> Annex ()
 setUrlMissing key url = do
-	addLog (urlLog key) =<< logNow InfoMissing url
+	addLog (urlLogFile key) =<< logNow InfoMissing url
 	whenM (null <$> getUrls key) $
 		logChange key webUUID InfoMissing