Generate shorter keys for WORM and URL, avoiding keys that are longer than used for SHA256, so as to not break on systems like Windows that have very small maximum path length limits.

Backend/URL.hs

@@ -32,10 +32,8 @@ backend = Backend
 
 {- Every unique url has a corresponding key. -}
 fromUrl :: String -> Maybe Integer -> Annex Key
-fromUrl url size = do
-	n <- genKeyName url
-	return $ stubKey
-		{ keyName = n
-		, keyBackendName = "URL"
-		, keySize = size
-		}
+fromUrl url size = return $ stubKey
+	{ keyName = genKeyName url
+	, keyBackendName = "URL"
+	, keySize = size
+	}

Backend/Utilities.hs

@@ -13,13 +13,18 @@ import Common.Annex
 
 {- Generates a keyName from an input string. Takes care of sanitizing it.
  - If it's not too long, the full string is used as the keyName.
- - Otherwise, it's truncated at half the filename length limit, and its
- - md5 is prepended to ensure a unique key. -}
-genKeyName :: String -> Annex String
-genKeyName s = do
-	limit <- liftIO . fileNameLengthLimit =<< fromRepo gitAnnexDir
-	let s' = preSanitizeKeyName s
-	let truncs = truncateFilePath (limit `div` 2) s'
-	return $ if s' == truncs
-		then s'
-		else truncs ++ "-" ++ md5s (Str s)
+ - Otherwise, it's truncated, and its md5 is prepended to ensure a unique
+ - key. -}
+genKeyName :: String -> String
+genKeyName s
+	-- Avoid making keys longer than the length of a SHA256 checksum.
+	| bytelen > sha256len =
+		truncateFilePath (sha256len - md5len - 1) s' ++ "-" ++ md5s (Str s)
+	| otherwise = s'
+  where
+	s' = preSanitizeKeyName s
+	bytelen = length (decodeW8 s')
+
+	sha256len = 64
+	md5len = 32
+

Backend/WORM.hs

@@ -34,9 +34,8 @@ keyValue :: KeySource -> Annex (Maybe Key)
 keyValue source = do
 	stat <- liftIO $ getFileStatus $ contentLocation source
 	relf <- getTopFilePath <$> inRepo (toTopFilePath $ keyFilename source)
-	n <- genKeyName relf
 	return $ Just $ stubKey
-		{ keyName = n
+		{ keyName = genKeyName relf
 		, keyBackendName = name backend
 		, keySize = Just $ fromIntegral $ fileSize stat
 		, keyMtime = Just $ modificationTime stat

debian/changelog

@@ -12,6 +12,9 @@ git-annex (5.20141232) UNRELEASED; urgency=medium
   * Check git version at runtime, rather than assuming it will be the same
     as the git version used at build time when running git-checkattr and
     git-branch remove.
+  * Generate shorter keys for WORM and URL, avoiding keys that are longer
+    than used for SHA256, so as to not break on systems like Windows that
+    have very small maximum path length limits.
 
  -- Joey Hess <id@joeyh.name>  Fri, 02 Jan 2015 13:35:13 -0400