add INPUT-REQUIRED

Used by git-annex-compute-singularity to make addcomputed --fast work.

Also, simplified git-annex-compute-singularity; there is no need to hard
link the container into place. singularity does not care about the
extension of the container, so can just pass it the annex object file.

Remote/Compute.hs

@@ -201,17 +201,19 @@ programField = Accepted "program"
 data ProcessCommand
 	= ProcessInput FilePath
 	| ProcessOutput FilePath
+	| ProcessProgress PercentFloat
 	| ProcessReproducible
 	| ProcessSandbox
-	| ProcessProgress PercentFloat
+	| ProcessInputRequired FilePath
 	deriving (Show, Eq)
 
 instance Proto.Receivable ProcessCommand where
 	parseCommand "INPUT" = Proto.parse1 ProcessInput
 	parseCommand "OUTPUT" = Proto.parse1 ProcessOutput
+	parseCommand "PROGRESS" = Proto.parse1 ProcessProgress
 	parseCommand "REPRODUCIBLE" = Proto.parse0 ProcessReproducible
 	parseCommand "SANDBOX" = Proto.parse0 ProcessSandbox
-	parseCommand "PROGRESS" = Proto.parse1 ProcessProgress
+	parseCommand "INPUT-REQUIRED" = Proto.parse1 ProcessInputRequired
 	parseCommand _ = Proto.parseFail
 
 newtype PercentFloat = PercentFloat Float
@@ -392,9 +394,10 @@ runComputeProgram
 	:: ComputeProgram
 	-> ComputeState
 	-> ImmutableState
-	-> (OsPath -> Annex (Key, Maybe (Either Git.Sha OsPath)))
-	-- ^ get input file's content, or Nothing the input file's
-	-- content is not available
+	-> (OsPath -> Bool -> Annex (Key, Maybe (Either Git.Sha OsPath)))
+	-- ^ Get input file's content, or Nothing the input file's
+	-- content is not available. True is passed when the input content
+	-- is required even for addcomputed --fast.
 	-> Maybe (Key, MeterUpdate)
 	-- ^ update meter for this key
 	-> (ComputeProgramResult -> OsPath -> NominalDiffTime -> Annex v)
@@ -454,37 +457,8 @@ runComputeProgram (ComputeProgram program) state (ImmutableState immutablestate)
 		liftIO $ hFlush (stdinHandle p)
 
 	parseoutput p tmpdir subdir result meterfile l = case Proto.parseMessage l of
-		Just (ProcessInput f) -> do
-			let f' = toOsPath f
-			let knowninput = M.member f'
-				(computeInputs (computeState result))
-			checksafefile tmpdir subdir f' "input"
-			checkimmutable knowninput "inputting" f' $ do
-				(k, inputcontent) <- getinputcontent f'
-				let mkrel a = Just <$> 
-					(a >>= liftIO . relPathDirToFile subdir)
-				mp <- case inputcontent of
-					Nothing -> pure Nothing
-					Just (Right obj)
-						| computeSandbox result -> 
-							mkrel $ populatesandbox obj tmpdir
-						| otherwise ->
-							mkrel $ pure obj
-					Just (Left gitsha) -> 
-						mkrel $ populategitsha gitsha tmpdir
-				sendresponse p $
-					maybe "" fromOsPath mp
-				let result' = result
-					{ computeInputsUnavailable = 
-						isNothing mp || computeInputsUnavailable result
-					}
-				return $ if immutablestate
-					then result'
-					else modresultstate result' $ \s -> s
-						{ computeInputs = 
-							M.insert f' k
-								(computeInputs s)
-						}
+		Just (ProcessInput f) -> handleinput f False p tmpdir subdir result
+		Just (ProcessInputRequired f) -> handleinput f True p tmpdir subdir result
 		Just (ProcessOutput f) -> do
 			let f' = toOsPath f
 			checksafefile tmpdir subdir f' "output"
@@ -525,6 +499,38 @@ runComputeProgram (ComputeProgram program) state (ImmutableState immutablestate)
 		Nothing -> giveup $
 			program ++ " output an unparseable line: \"" ++ l ++ "\""
 
+	handleinput f required p tmpdir subdir result = do
+		let f' = toOsPath f
+		let knowninput = M.member f'
+			(computeInputs (computeState result))
+		checksafefile tmpdir subdir f' "input"
+		checkimmutable knowninput "inputting" f' $ do
+			(k, inputcontent) <- getinputcontent f' required
+			let mkrel a = Just <$> 
+				(a >>= liftIO . relPathDirToFile subdir)
+			mp <- case inputcontent of
+				Nothing -> pure Nothing
+				Just (Right obj)
+					| computeSandbox result -> 
+						mkrel $ populatesandbox obj tmpdir
+					| otherwise ->
+						mkrel $ pure obj
+				Just (Left gitsha) -> 
+					mkrel $ populategitsha gitsha tmpdir
+			sendresponse p $
+				maybe "" fromOsPath mp
+			let result' = result
+				{ computeInputsUnavailable = 
+					isNothing mp || computeInputsUnavailable result
+				}
+			return $ if immutablestate
+				then result'
+				else modresultstate result' $ \s -> s
+					{ computeInputs = 
+						M.insert f' k
+							(computeInputs s)
+					}
+
 	modresultstate result f = 
 		result { computeState = f (computeState result) }
 
@@ -630,7 +636,7 @@ computeKey rs (ComputeProgram program) k _af dest meterupdate vc =
 			(Just (k, p))
 			(postcompute keyfile)
 
-	getinputcontent state f =
+	getinputcontent state f _required =
 		case M.lookup f (computeInputs state) of
 			Just inputkey -> case keyGitSha inputkey of
 				Nothing ->