fix fileJournal

My ByteString rewrite oversimplified it, resulting in any _ in a journal
file turning into a / in the git-annex branch, which was often the wrong
filename, or sometimes (//) an invalid filename that git
refused to add.

Annex/Journal.hs

@@ -100,29 +100,38 @@ journalDirty = do
 			`catchIO` (const $ doesDirectoryExist d)
 
 {- Produces a filename to use in the journal for a file on the branch.
- -
- - The input filename is assumed to not contain any '_' character,
- - since path separators are replaced with that.
  -
  - The journal typically won't have a lot of files in it, so the hashing
  - used in the branch is not necessary, and all the files are put directly
  - in the journal directory.
  -}
 journalFile :: RawFilePath -> Git.Repo -> RawFilePath
-journalFile file repo = gitAnnexJournalDir' repo P.</> S.map mangle file
+journalFile file repo = gitAnnexJournalDir' repo P.</> S.concatMap mangle file
   where
 	mangle c
-		| P.isPathSeparator c = fromIntegral (ord '_')
-		| otherwise = c
+		| P.isPathSeparator c = S.singleton underscore
+		| c == underscore = S.pack [underscore, underscore]
+		| otherwise = S.singleton c
+	underscore = fromIntegral (ord '_')
 
 {- Converts a journal file (relative to the journal dir) back to the
  - filename on the branch. -}
 fileJournal :: RawFilePath -> RawFilePath
-fileJournal = S.map unmangle
+fileJournal = go
   where
-	unmangle c
-		| c == fromIntegral (ord '_') = P.pathSeparator
-		| otherwise = c
+	go b = 
+		let (h, t) = S.break (== underscore) b
+		in h <> case S.uncons t of
+			Nothing -> t
+			Just (_u, t') -> case S.uncons t' of
+				Nothing -> t'			
+				Just (w, t'')
+					| w == underscore ->
+						S.cons underscore (go t'')
+					| otherwise -> 
+						S.cons P.pathSeparator (go t')
+	
+	underscore = fromIntegral (ord '_')
 
 {- Sentinal value, only produced by lockJournal; required
  - as a parameter by things that need to ensure the journal is

doc/todo/optimize_by_converting_String_to_ByteString.mdwn

@@ -11,24 +11,10 @@ than find so the improvement is not as large.
 
 The `bs` branch is in a mergeable state now, but still needs work:
 
-* There's a bug impacting WORM keys with / in the keyname.
-  The files stored in the git-annex branch used to have the `/` changed
-  to `_`, but on the bs branch that does not happen. git also outputs
-  a message about "Ignoring" the file.
-
-  Test case:
-
-  git config annex.backend WORM
-  git annex addurl http://localhost/~joey/index.html
-
-  Hmm, that prints out the Ignoring message, and the file does not get
-  written to the git-annex branch. But in my big repo, I saw the message
-  and saw a file in the branch, with `/` in its keyname. Earlier in the
-  branch, the same key used `_`. (Look for "36bfe385607b32c4d5150404c0" to
-  find it again.)
-
 * Profile various commands and look for hot spots.
 
+* ByteString.Char8.putStrLn may truncate?
+
 * Eliminate all the fromRawFilePath, toRawFilePath, encodeBS,
   decodeBS conversions. Or at least most of them. There are likely
   some places where a value is converted back and forth several times.