improve importfeed --force; try to match existing files to avoid unncessary duplication

Command/ImportFeed.hs

@@ -104,41 +104,63 @@ downloadFeed url = do
 downloadEnclosure :: Bool -> Cache -> ToDownload -> Annex ()
 downloadEnclosure relaxed cache enclosure
 	| S.member url (knownurls cache) =
-		whenM (Annex.getState Annex.force) go
+		whenM forced go
 	| otherwise = go
   where
+  	forced = Annex.getState Annex.force
   	url = location enclosure
 	go = do
-		dest <- liftIO $ feedFile (template cache) enclosure
-		showStart "addurl" dest
-		ifM (addUrlFile relaxed url dest)
-			( showEndOk
-			, showEndFail
+		dest <- makeunique (1 :: Integer) $ feedFile (template cache) enclosure
+		case dest of
+			Nothing -> noop
+			Just f -> do
+				showStart "addurl" f
+				ifM (addUrlFile relaxed url f)
+					( showEndOk
+					, showEndFail
+					)
+	{- Find a unique filename to save the url to.
+	 - If the file exists, prefixes it with a number.
+	 - When forced, the file may already exist and have the same
+	 - url, in which case Nothing is returned as it does not need
+	 - to be re-downloaded. -}
+	makeunique n file = ifM alreadyexists
+		( ifM forced
+			( ifAnnexed f checksameurl tryanother
+			, tryanother
+			)
+		, return $ Just f
+		)
+	  where
+	  	f = if n < 2
+			then file
+			else
+				let (d, base) = splitFileName file
+				in d </> show n ++ "_" ++ base
+		tryanother = makeunique (n + 1) file
+		alreadyexists = liftIO $ isJust <$> catchMaybeIO (getSymbolicLinkStatus f)
+		checksameurl (k, _) = ifM (elem url <$> getUrls k)
+			( return Nothing
+			, tryanother
 			)
 	
 defaultTemplate :: String
 defaultTemplate = "${feedtitle}/${itemtitle}${extension}"
 
-{- Generate a unique filename for the feed item by filling 
- - out the template.
- -
- - Since each feed url is only downloaded once,
- - if the file already exists, two items with different urls
- - are conflicting. A number is added to disambiguate.
- -}
-feedFile :: Utility.Format.Format -> ToDownload -> IO FilePath
-feedFile tmpl i = makeUnique 1 $
-	Utility.Format.format tmpl $ M.fromList
-		[ field "feedtitle" $ getFeedTitle $ feed i
-		, fieldMaybe "itemtitle" $ getItemTitle $ item i
-		, fieldMaybe "feedauthor" $ getFeedAuthor $ feed i
-		, fieldMaybe "itemauthor" $ getItemAuthor $ item i
-		, fieldMaybe "itemsummary" $ getItemSummary $ item i
-		, fieldMaybe "itemdescription" $ getItemDescription $ item i
-		, fieldMaybe "itemrights" $ getItemRights $ item i
-		, fieldMaybe "itemid" $ snd <$> getItemId (item i)
-		, ("extension", map sanitize $ takeExtension $ location i)
-		]
+{- Generates a filename to use for a feed item by filling out the template.
+ - The filename may not be unique. -}
+feedFile :: Utility.Format.Format -> ToDownload -> FilePath
+feedFile tmpl i = Utility.Format.format tmpl $ M.fromList
+	[ field "feedtitle" $ getFeedTitle $ feed i
+	, fieldMaybe "itemtitle" $ getItemTitle $ item i
+	, fieldMaybe "feedauthor" $ getFeedAuthor $ feed i
+	, fieldMaybe "itemauthor" $ getItemAuthor $ item i
+	, fieldMaybe "itemsummary" $ getItemSummary $ item i
+	, fieldMaybe "itemdescription" $ getItemDescription $ item i
+	, fieldMaybe "itemrights" $ getItemRights $ item i
+	, fieldMaybe "itemid" $ snd <$> getItemId (item i)
+	, ("extension", map sanitize $ takeExtension $ location i)
+	]
   where
 	field k v = 
 		let s = map sanitize v in
@@ -149,16 +171,3 @@ feedFile tmpl i = makeUnique 1 $
 	sanitize c
 		| isSpace c || isPunctuation c || c == '/' = '_'
 		| otherwise = c
-
-makeUnique :: Integer -> FilePath -> IO FilePath
-makeUnique n file =
-	ifM (isJust <$> catchMaybeIO (getSymbolicLinkStatus f))
-		( makeUnique (n + 1) file
-		, return f
-		)
-  where
-  	f = if n < 2
-		then file
-		else
-			let (d, base) = splitFileName file
-			in d </> show n ++ "_" ++ base

doc/git-annex.mdwn

@@ -195,7 +195,7 @@ subdirectories).
   Imports the contents of podcast feeds. Only downloads files whose
   urls have not already been added to the repository before, so you can
   delete, rename, etc the resulting files and repeated runs won't duplicate
-  them. (Use --force to force downloading files it's seen before.)
+  them. (Use --force to force downloading urls it's seen before.)
 
   Use --template to control where the files are stored.
   The default template is '${feedtitle}/${itemtitle}${extension}'