safer inannex checking

git-annex-shell inannex now returns always 0, 1, or 100 (the last when
it's unclear if content is currently in the index due to it currently being
moved or dropped).

(Actual locking code still not yet written.)

Remote/Bup.hs

@@ -139,17 +139,21 @@ remove _ = do
  - in a bup repository. One way it to check if the git repository has
  - a branch matching the name (as created by bup split -n).
  -}
-checkPresent :: Git.Repo -> Git.Repo -> Key -> Annex (Either IOException Bool)
+checkPresent :: Git.Repo -> Git.Repo -> Key -> Annex (Either String Bool)
 checkPresent r bupr k
 	| Git.repoIsUrl bupr = do
 		showAction $ "checking " ++ Git.repoDescribe r
 		ok <- onBupRemote bupr boolSystem "git" params
 		return $ Right ok
-	| otherwise = liftIO $ try $ boolSystem "git" $ Git.gitCommandLine params bupr
+	| otherwise = dispatch <$> localcheck
 	where
 		params = 
 			[ Params "show-ref --quiet --verify"
 			, Param $ "refs/heads/" ++ show k]
+		localcheck = liftIO $ try $
+			boolSystem "git" $ Git.gitCommandLine params bupr
+		dispatch (Left e) = Left $ show e
+		dispatch (Right v) = Right v
 
 {- Store UUID in the annex.uuid setting of the bup repository. -}
 storeBupUUID :: UUID -> BupRepo -> Annex ()

Remote/Directory.hs

@@ -114,5 +114,9 @@ remove d k = liftIO $ catchBool $ do
 		file = dirKey d k
 		dir = parentDir file
 
-checkPresent :: FilePath -> Key -> Annex (Either IOException Bool)
-checkPresent d k = liftIO $ try $ doesFileExist (dirKey d k)
+checkPresent :: FilePath -> Key -> Annex (Either String Bool)
+checkPresent d k = dispatch <$> check
+	where
+		check = liftIO $ try $ doesFileExist (dirKey d k)
+		dispatch (Left e) = Left $ show e
+		dispatch (Right v) = Right v

Remote/Git.hs

@@ -125,22 +125,38 @@ tryGitConfigRead r
 				else old : exchange ls new
 
 {- Checks if a given remote has the content for a key inAnnex.
- - If the remote cannot be accessed, returns a Left error.
+ - If the remote cannot be accessed, or if it cannot determine
+ - whether it has the content, returns a Left error message.
  -}
-inAnnex :: Git.Repo -> Key -> Annex (Either IOException Bool)
+inAnnex :: Git.Repo -> Key -> Annex (Either String Bool)
 inAnnex r key
-	| Git.repoIsHttp r = safely checkhttp
+	| Git.repoIsHttp r = checkhttp
 	| Git.repoIsUrl r = checkremote
-	| otherwise = safely checklocal
+	| otherwise = checklocal
 	where
-		checklocal = onLocal r $ Annex.Content.inAnnex key
+		checkhttp = dispatch <$> check
+			where
+				check = safely $ Url.exists $ keyUrl r key
+				dispatch (Left e) = Left $ show e
+				dispatch (Right v) = Right v
 		checkremote = do
 			showAction $ "checking " ++ Git.repoDescribe r
-			inannex <- onRemote r (boolSystem, False) "inannex" 
-				[Param (show key)]
-			return $ Right inannex
-		checkhttp = Url.exists $ keyUrl r key
-		safely a = liftIO (try a ::IO (Either IOException Bool))
+			onRemote r (check, unknown) "inannex" [Param (show key)]
+			where
+				check c p = dispatch <$> safeSystem c p
+				dispatch ExitSuccess = Right True
+				dispatch (ExitFailure 1) = Right False
+				dispatch _ = unknown
+		checklocal = dispatch <$> check
+			where
+				check = safely $ onLocal r $
+					Annex.Content.inAnnexSafe key
+				dispatch (Left e) = Left $ show e
+				dispatch (Right (Just b)) = Right b
+				dispatch (Right Nothing) = unknown
+		safely :: IO a -> Annex (Either IOException a)
+		safely a = liftIO $ try a
+		unknown = Left $ "unable to check " ++ Git.repoDescribe r
 
 {- Runs an action on a local repository inexpensively, by making an annex
  - monad using that repository. -}

Remote/Hook.hs

@@ -119,14 +119,16 @@ retrieveEncrypted h (cipher, enck) f = withTmp enck $ \tmp ->
 remove :: String -> Key -> Annex Bool
 remove h k = runHook h "remove" k Nothing $ return True
 
-checkPresent :: Git.Repo -> String -> Key -> Annex (Either IOException Bool)
+checkPresent :: Git.Repo -> String -> Key -> Annex (Either String Bool)
 checkPresent r h k = do
 	showAction $ "checking " ++ Git.repoDescribe r
 	v <- lookupHook h "checkpresent"
-	liftIO (try (check v) ::IO (Either IOException Bool))
+	dispatch <$> liftIO (try (check v) ::IO (Either IOException Bool))
 	where
 		findkey s = show k `elem` lines s
 		env = hookEnv k Nothing
+		dispatch (Left e) = Left $ show e
+		dispatch (Right v) = Right v
 		check Nothing = error "checkpresent hook misconfigured"
 		check (Just hook) = do
 			(frompipe, topipe) <- createPipe

Remote/Rsync.hs

@@ -128,7 +128,7 @@ remove o k = withRsyncScratchDir $ \tmp -> do
 		, Param $ rsyncKeyDir o k
 		]
 
-checkPresent :: Git.Repo -> RsyncOpts -> Key -> Annex (Either IOException Bool)
+checkPresent :: Git.Repo -> RsyncOpts -> Key -> Annex (Either String Bool)
 checkPresent r o k = do
 	showAction $ "checking " ++ Git.repoDescribe r
 	-- note: Does not currently differnetiate between rsync failing

Remote/S3real.hs

@@ -172,7 +172,7 @@ remove r k = s3Action r False $ \(conn, bucket) -> do
 	res <- liftIO $ deleteObject conn $ bucketKey r bucket k
 	s3Bool res
 
-checkPresent :: Remote Annex -> Key -> Annex (Either IOException Bool)
+checkPresent :: Remote Annex -> Key -> Annex (Either String Bool)
 checkPresent r k = s3Action r noconn $ \(conn, bucket) -> do
 	showAction $ "checking " ++ name r
 	res <- liftIO $ getObjectInfo conn $ bucketKey r bucket k

Remote/Web.hs

@@ -64,7 +64,7 @@ dropKey _ = do
 	warning "removal from web not supported"
 	return False
 
-checkKey :: Key -> Annex (Either IOException Bool)
+checkKey :: Key -> Annex (Either String Bool)
 checkKey key = do
 	us <- getUrls key
 	if null us