rename to annexobjects location on unexport

This avoids needing to re-upload the file again to get it to the
annexobjects location, which git-annex sync was doing when it was
preferred content.

If the file is not preferred content, sync will drop it from the
annexobjects location.

If the file has been deleted from the tree, it will remain in the
annexobjects location until an unused/dropunused pass is done.

Annex/Locations.hs

@@ -28,6 +28,7 @@ module Annex.Locations (
 	annexLocationsBare,
 	annexLocationsNonBare,
 	annexLocation,
+	exportAnnexObjectLocation,
 	gitAnnexDir,
 	gitAnnexObjectDir,
 	gitAnnexTmpOtherDir,
@@ -122,6 +123,7 @@ import Types.UUID
 import Types.GitConfig
 import Types.Difference
 import Types.BranchState
+import Types.Export
 import qualified Git
 import qualified Git.Types as Git
 import Git.FilePath
@@ -170,6 +172,13 @@ annexLocationsBare config key =
 annexLocation :: GitConfig -> Key -> (HashLevels -> Hasher) -> RawFilePath
 annexLocation config key hasher = objectDir P.</> keyPath key (hasher $ objectHashLevels config)
 
+{- For exportree remotes with annexobjects=true, objects are stored
+ - in this location as well as in the exported tree. -}
+exportAnnexObjectLocation :: GitConfig -> Key -> ExportLocation
+exportAnnexObjectLocation gc k =
+	mkExportLocation $
+		".git" P.</> annexLocation gc k hashDirLower
+
 {- Number of subdirectories from the gitAnnexObjectDir
  - to the gitAnnexLocation. -}
 gitAnnexLocationDepth :: GitConfig -> Int

Command/Export.hs

@@ -152,16 +152,15 @@ changeExport r db (ExportFiltered new) = do
 		[oldtreesha] -> do
 			diffmap <- mkDiffMap oldtreesha new db
 			let seekdiffmap a = mapM_ a (M.toList diffmap)
-			-- Rename old files to temp, or delete.
-			let deleteoldf = \ek oldf -> commandAction $
-				startUnexport' r db oldf ek
+			let disposeoldf = \ek oldf -> commandAction $
+				startDispose r db oldf ek
 			seekdiffmap $ \case
 				(ek, (oldf:oldfs, _newf:_)) -> do
 					commandAction $
 						startMoveToTempName r db oldf ek
-					forM_ oldfs (deleteoldf ek)
+					forM_ oldfs (disposeoldf ek)
 				(ek, (oldfs, [])) ->
-					forM_ oldfs (deleteoldf ek)
+					forM_ oldfs (disposeoldf ek)
 				(_ek, ([], _)) -> noop
 			waitForAllRunningCommandActions
 			-- Rename from temp to new files.
@@ -350,16 +349,6 @@ startUnexport r db f shas = do
 	ai = ActionItemTreeFile f'
 	si = SeekInput []
 
-startUnexport' :: Remote -> ExportHandle -> TopFilePath -> Key -> CommandStart
-startUnexport' r db f ek =
-	starting ("unexport " ++ name r) ai si $
-		performUnexport r db [ek] loc
-  where
-	loc = mkExportLocation f'
-	f' = getTopFilePath f
-	ai = ActionItemTreeFile f'
-	si = SeekInput []
-
 -- Unlike a usual drop from a repository, this does not check that
 -- numcopies is satisfied before removing the content. Typically an export
 -- remote is untrusted, so would not count as a copy anyway.
@@ -401,6 +390,23 @@ cleanupUnexport r db eks loc = do
 	
 	removeEmptyDirectories r db loc eks
 
+-- Dispose of an old exported file by either unexporting it, or by moving
+-- it to the annexobjects location.
+startDispose :: Remote -> ExportHandle -> TopFilePath -> Key -> CommandStart
+startDispose r db f ek =
+	starting ("unexport " ++ name r) ai si $
+		if annexObjects (Remote.config r) && not (isGitShaKey ek)
+			then do
+				gc <- Annex.getGitConfig
+				performRename r db ek loc
+					(exportAnnexObjectLocation gc ek)
+			else performUnexport r db [ek] loc
+  where
+	loc = mkExportLocation f'
+	f' = getTopFilePath f
+	ai = ActionItemTreeFile f'
+	si = SeekInput []
+
 startRecoverIncomplete :: Remote -> ExportHandle -> Git.Sha -> TopFilePath -> CommandStart
 startRecoverIncomplete r db sha oldf
 	| sha `elem` nullShas = stop

Remote/Helper/ExportImport.hs

@@ -408,10 +408,7 @@ adjustExportImport' isexport isimport annexobjects r rs gc = do
 			k loc 
 			=<< getkeycids ciddbv k
 
-	-- For annexobjects=true, objects are stored in the remote
-	-- in a location under .git/objects/
-	annexobjectlocation k = mkExportLocation $
-		".git" P.</> annexLocation gc k hashDirLower
+	annexobjectlocation k = exportAnnexObjectLocation gc k
 
 	checkpresentannexobject k = 
 		checkPresentExport (exportActions r) k (annexobjectlocation k)

doc/todo/git-annex_proxies.mdwn

@@ -33,12 +33,20 @@ Planned schedule of work:
 * Working on `exportreeplus` branch which is groundwork for proxying to
   exporttree=yes special remotes.
 
-* `git-annex export` when unexporting a deleted file from the tree should
-  rename it to the annexobjects location. This would avoid needing to
-  re-upload it again in the case where it's preferred content of the
-  remote. Currently eg, a sync will unexport the file and then re-upload
-  it. If it's not preferred content, sync will drop it from the
-  annexobjects location.
+* `git-annex export` when exporting a file should rename it from the
+  annexobjects location when it's present there. This will avoid redundant
+  uploads.
+
+  An example case where this is important: Proxying to a exporttree remote,
+  a file is uploaded to it but is not yet in an exported tree. When the
+  exported tree is pushed, the remote needs to be updated by exporting to
+  it. In this case, the proxy doesn't have a copy of the file, so it would
+  need to download it from annexobjects before uploading it to the final
+  location. With this optimisation, it can just rename it.
+
+  However: If a key is used twice in an exported tree, it seems a proxy
+  will need to download and reupload anyway. Unless a copy operation is
+  added to exporttree remotes..
 
 ## items deferred until later for p2p protocol over http