upload progress bar for git remote on same filesystem

cp is used here, but we can just watch the size of the destination file

This commit made from within the ruins of an old mill, overlooking a
beautiful waterfall.

Assistant/Threads/TransferPoller.hs

@@ -45,5 +45,6 @@ transferPollerThread st dstatus = thread $ do
 				when (bytesComplete info /= sz && isJust sz) $
 					alterTransferInfo dstatus t $
 						\i -> i { bytesComplete = sz }
-			{- can't poll uploads -}
+			{- Can't poll uploads, instead the upload code
+			 - updates the files. -}
 			| otherwise = noop