In .gitattributes, the git-annex-numcopies attribute can be used to control the number of copies to retain of different types of files.

Command/Drop.hs

@@ -15,24 +15,27 @@ import LocationLog
 import Types
 import Core
 import Messages
+import Utility
 
 seek :: [SubCmdSeek]
-seek = [withFilesInGit start]
+seek = [withAttrFilesInGit "git-annex-numcopies" start]
 
 {- Indicates a file's content is not wanted anymore, and should be removed
  - if it's safe to do so. -}
-start :: SubCmdStartString
-start file = isAnnexed file $ \(key, backend) -> do
+start :: SubCmdStartAttrFile
+start (file, attr) = isAnnexed file $ \(key, backend) -> do
 	inbackend <- Backend.hasKey key
 	if not inbackend
 		then return Nothing
 		else do
 			showStart "drop" file
-			return $ Just $ perform key backend
+			return $ Just $ perform key backend numcopies
+	where
+		numcopies = readMaybe attr :: Maybe Int
 
-perform :: Key -> Backend -> SubCmdPerform
-perform key backend = do
-	success <- Backend.removeKey backend key
+perform :: Key -> Backend -> Maybe Int -> SubCmdPerform
+perform key backend numcopies = do
+	success <- Backend.removeKey backend key numcopies
 	if success
 		then return $ Just $ cleanup key
 		else return Nothing