fix annex.skipunknown false error propagation

Propagate nonzero exit status from git ls-files when a specified file does
not exist, or a specified directory does not contain any files checked into
git.

The recent completion of the annex.skipunknown transition exposed this
bug, that has unfortunately been lurking all along.

It is also possible that git ls-files errors out for some other reason
-- perhaps a permission problem -- and this will also fix error propagation
in such situations.

Sponsored-by: Dartmouth College's Datalad project

CmdLine/Seek.hs

@@ -77,13 +77,13 @@ withFilesInGitAnnexNonRecursive ww needforce a (WorkTreeItems l) = ifM (Annex.ge
 		(fs, cleanup) <- inRepo $ LsFiles.inRepoDetails os [toRawFilePath p]
 		r <- case fs of
 			[f] -> do
-				void $ liftIO $ cleanup
+				propagateLsFilesError cleanup
 				fst <$> getfiles ((SeekInput [p], f):c) ps
 			[] -> do
-				void $ liftIO $ cleanup
+				propagateLsFilesError cleanup
 				fst <$> getfiles c ps
 			_ -> do
-				void $ liftIO $ cleanup
+				propagateLsFilesError cleanup
 				giveup needforce
 		return (r, pure True)
 withFilesInGitAnnexNonRecursive _ _ _ NoWorkTreeItems = noop
@@ -321,7 +321,7 @@ seekFiltered prefilter a listfs = do
 	checktimelimit <- mkCheckTimeLimit
 	(fs, cleanup) <- listfs
 	go matcher checktimelimit fs
-	liftIO $ void cleanup
+	propagateLsFilesError cleanup
   where
 	go _ _ [] = return ()
 	go matcher checktimelimit (v@(_si, f):rest) = checktimelimit noop $ do
@@ -373,7 +373,7 @@ seekFilteredKeys seeker listfs = do
 				)
 			join (liftIO (wait mdprocessertid))
 			join (liftIO (wait processertid))
-	liftIO $ void cleanup
+	propagateLsFilesError cleanup
   where
 	finisher mi oreader checktimelimit = liftIO oreader >>= \case
 		Just ((si, f), content) -> checktimelimit (liftIO discard) $ do
@@ -618,3 +618,8 @@ mkCheckTimeLimit = Annex.getState Annex.timelimit >>= \case
 				cleanup
 				liftIO $ exitWith $ ExitFailure 101
 			else a
+
+propagateLsFilesError :: IO Bool -> Annex ()
+propagateLsFilesError cleanup =
+	unlessM (liftIO cleanup) $
+		Annex.incError