only chunk stable keys

The content of unstable keys can potentially be different in different
repos, so eg, resuming a chunked upload started by another repo would
corrupt data.

Backend.hs

@@ -15,7 +15,7 @@ module Backend (
 	chooseBackend,
 	lookupBackendName,
 	maybeLookupBackendName,
-	checkStableKey,
+	isStableKey,
 ) where
 
 import Common.Annex
@@ -126,6 +126,6 @@ maybeLookupBackendName s = M.lookup s nameMap
 nameMap :: M.Map String Backend
 nameMap = M.fromList $ zip (map B.name list) list
 
-checkStableKey :: Key -> Bool
-checkStableKey k = maybe False (`B.isStableKey` k) 
+isStableKey :: Key -> Bool
+isStableKey k = maybe False (`B.isStableKey` k) 
 	(maybeLookupBackendName (keyBackendName k))

Remote/Helper/Chunked.hs

@@ -23,6 +23,7 @@ import Types.Key
 import Logs.Chunk
 import Utility.Metered
 import Crypto (EncKey)
+import Backend (isStableKey)
 import Annex.Exception
 
 import qualified Data.ByteString.Lazy as L
@@ -95,7 +96,7 @@ storeChunks
 	-> Annex Bool
 storeChunks u chunkconfig k f p storer checker = 
 	case chunkconfig of
-		(UnpaddedChunks chunksize) -> 
+		(UnpaddedChunks chunksize) | isStableKey k -> 
 			bracketIO open close (go chunksize)
 		_ -> showprogress $ storer k (FileContent f)
   where