Deal with stale mappings for deleted file in direct mode.

The most common way for a mapping to be stale is when a file was deleted,
or renamed. Nothing updates the mappings for deletions yet.
But they can also become stale in other ways. For example a file can
be modified.

So, the mapping is not trusted to be consistent. When we get a key,
only replace symlinks that still point to that key with its content.
When we drop a key, only put back symlinks for files that still have
the direct mode content.

Annex/Content.hs

@@ -247,8 +247,18 @@ moveAnnex key src = withObjectLoc key storeobject storedirect
 				freezeContent dest
 				freezeContentDir dest
 			)
-	storedirect [] = storeobject =<< inRepo (gitAnnexLocation key)
-	storedirect (dest:fs) = do
+	storedirect fs = storedirect' =<< liftIO (filterM validsymlink fs)
+
+	validsymlink f = do
+		tl <- tryIO $ readSymbolicLink f
+		return $ case tl of
+			Right l
+				| isLinkToAnnex l ->
+					Just key == fileKey (takeFileName l)
+			_ -> False
+
+	storedirect' [] = storeobject =<< inRepo (gitAnnexLocation key)
+	storedirect' (dest:fs) = do
 		updateCache key src
 		thawContent src
 		liftIO $ replaceFile dest $ moveFile src
@@ -345,9 +355,10 @@ removeAnnex key = withObjectLoc key remove removedirect
 			removeFile file
 		cleanObjectLoc key
 	removedirect fs = do
+		cache <- recordedCache key
 		removeCache key
-		mapM_ resetfile fs
-	resetfile f = do
+		mapM_ (resetfile cache) fs
+	resetfile cache f = whenM (compareCache f cache) $ do
 		l <- calcGitLink f key
 		top <- fromRepo Git.repoPath
 		cwd <- liftIO getCurrentDirectory

debian/changelog

@@ -9,6 +9,7 @@ git-annex (3.20130125) UNRELEASED; urgency=low
     and other tasks.
   * assistant: Ignore .DS_Store on OSX.
   * assistant: Fix location log when adding new file in direct mode.
+  * Deal with stale mappings for deleted file in direct mode.
 
  -- Joey Hess <joeyh@debian.org>  Sat, 26 Jan 2013 15:48:40 +1100
 

doc/design/assistant/desymlink.mdwn

@@ -87,6 +87,12 @@ is converted to a real file when it becomes present.
 * kqueue does not deliver an event when an existing file is modified.
   This doesn't affect OSX, which uses FSEvents now, but it makes direct
   mode assistant not 100% on other BSD's.
+* The mapping is not updated when files are deleted (or for the deletion
+  part of a rename). So it can contain old filenames that are no longer in
+  use. Code that uses the mapping has to take care to check that the
+  files they refer to exists, which is a good idea anyway. But,
+  it would be good to at some point update the mappings to remove deleted
+  files (fsck does this FWIW).
 
 ## done