finish up basic chunked remote groundwork

Chunk retrieval and reassembly, removal, and checking if all necessary
chunks are present.

This commit was sponsored by Damien Raude-Morvan.

Remote/Helper/Chunked/Legacy.hs

@@ -9,6 +9,7 @@ module Remote.Helper.Chunked.Legacy where
 
 import Common.Annex
 import Remote.Helper.Chunked
+import Utility.Metered
 
 import qualified Data.ByteString.Lazy as L
 import qualified Control.Exception as E
@@ -114,3 +115,12 @@ storeChunked chunksize dests storer content = either onerr return
 			let (chunk, b') = L.splitAt sz b
 			storer d chunk
 			storechunks sz (d:useddests) ds b'
+
+{- Writes a series of chunks to a file. The feeder is called to get
+ - each chunk.
+ -}
+meteredWriteFileChunks :: MeterUpdate -> FilePath -> [v] -> (v -> IO L.ByteString) -> IO ()
+meteredWriteFileChunks meterupdate dest chunks feeder =
+	withBinaryFile dest WriteMode $ \h ->
+		forM_ chunks $
+			meteredWrite meterupdate h <=< feeder