v6: Update associated files database when git has staged changes to pointer files

This commit was supported by the NSF-funded DataLad project.

CHANGELOG

@@ -11,6 +11,8 @@ git-annex (6.20180808) UNRELEASED; urgency=medium
     pipe. This also avoids git buffering the whole file content in memory.
   * v6: After updating the worktree for an add/drop, update git's index,
     so git status will not show the files as modified.
+  * v6: Update associated files database when git has staged changes
+    to pointer files.
   * linux standalone: When LOCPATH is already set, use it instead of the
     bundled locales. It can be set to an empty string to use the system
     locales too.

Database/Keys.hs

@@ -1,6 +1,6 @@
 {- Sqlite database of information about Keys
  -
- - Copyright 2015-2016 Joey Hess <id@joeyh.name>
+ - Copyright 2015-2018 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -31,9 +31,13 @@ import Annex.Common hiding (delete)
 import Annex.Version (versionUsesKeysDatabase)
 import qualified Annex
 import Annex.LockFile
+import Annex.CatFile
 import Utility.InodeCache
 import Annex.InodeSentinal
+import Git
 import Git.FilePath
+import Git.Command
+import Git.Types
 
 {- Runs an action that reads from the database.
  -
@@ -124,12 +128,16 @@ openDb createdb _ = catchPermissionDenied permerr $ withExclusiveLock gitAnnexKe
 			open db
 		(False, False) -> return DbUnavailable
   where
-	open db = liftIO $ DbOpen <$> H.openDbQueue H.MultiWriter db SQL.containedTable
 	-- If permissions don't allow opening the database, treat it as if
 	-- it does not exist.
 	permerr e = case createdb of
 		False -> return DbUnavailable
 		True -> throwM e
+	
+	open db = do
+		h <- liftIO $ H.openDbQueue H.MultiWriter db SQL.containedTable
+		reconcileStaged (SQL.WriteHandle h)
+		return $ DbOpen h
 
 {- Closes the database if it was open. Any writes will be flushed to it.
  -
@@ -172,3 +180,66 @@ getInodeCaches = runReaderIO . SQL.getInodeCaches . toIKey
 
 removeInodeCaches :: Key -> Annex ()
 removeInodeCaches = runWriterIO . SQL.removeInodeCaches . toIKey
+
+{- Looks at staged changes to find when unlocked files are copied/moved,
+ - and updates associated files in the keys database.
+ -
+ - Since staged changes can be dropped later, does not remove any
+ - associated files; only adds new associated files.
+ -
+ - This needs to be run before querying the keys database so that
+ - information is consistent with the state of the repository.
+ -
+ - TODO To avoid unncessary work, the index file is statted, and if it's not
+ - changed since last time this was run, nothing is done.
+ -}
+reconcileStaged :: SQL.WriteHandle -> Annex ()
+reconcileStaged h@(SQL.WriteHandle qh) = whenM versionUsesKeysDatabase $ do
+	(l, cleanup) <- inRepo $ pipeNullSplit diff
+	changed <- go l False
+	void $ liftIO cleanup
+	-- Flush database changes immediately so other processes can see them.
+	when changed $
+		liftIO $ H.flushDbQueue qh
+  where
+	diff =
+		-- Avoid using external diff command, which would be slow.
+		-- (The -G option may make it be used otherwise.)
+		[ Param "-c", Param "diff.external="
+		, Param "diff"
+		, Param "--cached"
+		, Param "--raw"
+		, Param "-z"
+		, Param "--abbrev=40"
+		-- Optimization: Only find pointer files. This is not
+		-- perfect. A file could start with this and not be a
+		-- pointer file. And a pointer file that is replaced with
+		-- a non-pointer file will match this.
+		, Param $ "-G^" ++ toInternalGitPath (pathSeparator:objectDir)
+		-- Don't include files that were deleted, because this only
+		-- wants to update information for files that are present
+		-- in the index.
+		, Param "--diff-filter=AMUT"
+		-- Disable rename detection.
+		, Param "--no-renames"
+		-- Avoid other complications.
+		, Param "--ignore-submodules=all"
+		, Param "--no-ext-diff"
+		]
+	
+	go (info:file:rest) changed = case words info of
+		((':':_srcmode):dstmode:_srcsha:dstsha:_change:[])
+			-- Only want files, not symlinks
+			| dstmode /= fmtTreeItemType TreeSymlink -> do
+				catKey (Ref dstsha) >>= \case
+					Nothing -> noop
+					Just k -> liftIO $ 
+						SQL.addAssociatedFileFast 
+							(toIKey k)
+							(asTopFilePath file)
+							h
+				go rest True
+			| otherwise -> go rest changed
+		_ -> return changed -- parse failed
+	go _ changed = return changed
+

doc/todo/smudge.mdwn

@@ -2,15 +2,18 @@ git-annex should use smudge/clean filters. v6 mode
 
 ### August sprint todo list
 
-* Reconcile staged changes into the associated files database, whenever
-  the database is queried. This is needed to handle eg:
+* Avoid running reconcileStaged when the index has not changed since last
+  time.
 
-	git add largefile
-	git mv largefile othername
-	git annex move othername --to foo
-	# fails to drop content from associated file othername,
-	# because it doesn't know it has that name
-	# git commit clears up this mess
+* If `git mv` of an unlocked file is run at the same time as `git annex drop`, 
+  and when git-annex starts up, the mv has not happened yet, but once it
+  wants to update the associated file to drop the content, the mv has 
+  happened, then the content will be left in the working tree despite
+  git-annex having said it dropped it.
+
+  I think git-annex fsck also won't notice this problem, even though,
+  once the mv is complete, git-annex does notice the change in the index 
+  and updates the associated files.
 
 * Checking out a different branch causes git to smudge all changed files,
   and write their content. This does not honor annex.thin. A warning