Preserve execute bits of unlocked files in v6 mode.

When annex.thin is set, adding an object will add the execute bits to the
work tree file, and this does mean that the annex object file ends up
executable.

This doesn't add any complexity that wasn't already present, because git
annex add of an executable file has always ingested it so that the annex
object ends up executable.

But, since an annex object file can be executable or not, when populating
an unlocked file from one, the executable bit is always added or removed
to match the mode of the pointer file.

Command/ReKey.hs

@@ -61,7 +61,7 @@ linkKey file oldkey newkey = ifM (isJust <$> isAnnexLink file)
 	 - and vulnerable to corruption. -}
 	( getViaTmp' DefaultVerify newkey $ \tmp -> unVerified $ do
 		oldobj <- calcRepo (gitAnnexLocation oldkey)
-		linkOrCopy' (return True) newkey oldobj tmp
+		linkOrCopy' (return True) newkey oldobj tmp Nothing
 	, do
 		ic <- withTSDelta (liftIO . genInodeCache file)
 	 	{- The file being rekeyed is itself an unlocked file, so if
@@ -69,7 +69,7 @@ linkKey file oldkey newkey = ifM (isJust <$> isAnnexLink file)
 		oldobj <- calcRepo (gitAnnexLocation oldkey)
 		v <- tryNonAsync $ modifyContent oldobj $ do
 			replaceFile oldobj $ \tmp ->
-				unlessM (checkedCopyFile oldkey file tmp) $
+				unlessM (checkedCopyFile oldkey file tmp Nothing) $
 					error "can't lock old key"
 			freezeContent oldobj
 			oldic <- withTSDelta (liftIO . genInodeCache oldobj)
@@ -95,9 +95,10 @@ cleanup file oldkey newkey = do
 			liftIO $ removeFile file
 			addLink file newkey Nothing
 		, do
+			mode <- liftIO $ catchMaybeIO $ fileMode <$> getFileStatus file
 			liftIO $ whenM (isJust <$> isPointerFile file) $
-				writeFile file (formatPointer newkey)
-			stagePointerFile file =<< hashPointerFile newkey
+				writePointerFile file newkey mode
+			stagePointerFile file mode =<< hashPointerFile newkey
 			Database.Keys.removeAssociatedFile oldkey 
 				=<< inRepo (toTopFilePath file)
 		)