assistant: Fix bug that could cause direct mode files to be unstaged from git.

My test case for this bug is to have the assistant running and syncing to
a remote, and create a file in the annex. Then at the command line run
git annex drop. The assistant sees that the file is gone, sees it's a wanted
file, and downloads it from the remote.

With a directory special remote and a small file, I was seeing around 1
time in 3, a race where the file got unstaged from git after it got
downloaded.

Looking at what direct mode content managing code does in this case, it
deletes the symlink, and then adds the file content back. It would be
possible, sometimes, to avoid removing the symlink and do this atomically.
And I probably should.. but in some cases, particularly where the file
needs to be run through `cp` (multiple direct mode files with same
content), there's no way to atomically replace the symlink with the
content.

Anyway, the bug turns out to be something that the watcher does right for
indirect mode, but not for direct mode. When it got an add event, it
checked to see if this was a new file, or one we've already added. In the
latter case, no add event was queued. But that means that only the rm event
is queued, and so it unstages the file.

Fixed by queueing an add event even when the file is already in git.

Tested by running hundreds of drops in a loop; file remained staged.

diff --git a/Assistant/Threads/Watcher.hs b/Assistant/Threads/Watcher.hs
index c2ba90ebe4551d40fa31b1ca2d269101dfca3ee0..89cef6ea76b7931c820260c06195264b864e8705 100644 (file)
--- a/Assistant/Threads/Watcher.hs
+++ b/Assistant/Threads/Watcher.hs
@@ -184,8 +184,11 @@ onAdd matcher file filestatus
        | otherwise = noChange
 
 {- In direct mode, add events are received for both new files, and
- - modified existing files. Or, in some cases, existing files that have not
- - really been modified. -}
+ - modified existing files.
+ -
+ - It's possible to get an add event for an existing file that is not
+ - really modified, but it might have just been deleted and been put back,
+ - so it's restaged to make sure. -}
 onAddDirect :: FileMatcher -> Handler
 onAddDirect matcher file fs = do
        debug ["add direct", file]
@@ -193,7 +196,7 @@ onAddDirect matcher file fs = do
        case (v, fs) of
                (Just key, Just filestatus) ->
                        ifM (liftAnnex $ sameFileStatus key filestatus)
-                               ( noChange
+                               ( add matcher file
                                , do
                                        liftAnnex $ changedDirect key file
                                        add matcher file

diff --git a/debian/changelog b/debian/changelog
index 763e3577f92c834e23849804e44efe80bd1113b2..dc602e9e2bf6692647821e882d4c33104d91e592 100644 (file)
--- a/debian/changelog
+++ b/debian/changelog
@@ -24,6 +24,8 @@ git-annex (4.20130324) UNRELEASED; urgency=low
     and unwanted repositories.
   * drop --auto: Fix bug that prevented dropping files from untrusted
     repositories.
+  * assistant: Fix bug that could cause direct mode files to be unstaged
+    from git.
 
  -- Joey Hess <joeyh@debian.org>  Mon, 25 Mar 2013 10:21:46 -0400