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