Avoid backtraces on expected failures when built with ghc 8; only use backtraces for unexpected errors.

ghc 8 added backtraces on uncaught errors. This is great, but git-annex was
using error in many places for a error message targeted at the user, in
some known problem case. A backtrace only confuses such a message, so omit it.

Notably, commands like git annex drop that failed due to eg, numcopies,
used to use error, so had a backtrace.

This commit was sponsored by Ethan Aubin.

1 files changed, 4 insertions, 4 deletions

diff --git a/Remote/Hook.hs b/Remote/Hook.hs
index 7d8f7f096..6abffe117 100644
--- a/Remote/Hook.hs
+++ b/Remote/Hook.hs
@@ -68,12 +68,12 @@ gen r u c gc = do
 			, checkUrl = Nothing
 			}
   where
-	hooktype = fromMaybe (error "missing hooktype") $ remoteAnnexHookType gc
+	hooktype = fromMaybe (giveup "missing hooktype") $ remoteAnnexHookType gc
 
 hookSetup :: Maybe UUID -> Maybe CredPair -> RemoteConfig -> RemoteGitConfig -> Annex (RemoteConfig, UUID)
 hookSetup mu _ c gc = do
 	u <- maybe (liftIO genUUID) return mu
-	let hooktype = fromMaybe (error "Specify hooktype=") $
+	let hooktype = fromMaybe (giveup "Specify hooktype=") $
 		M.lookup "hooktype" c
 	(c', _encsetup) <- encryptionSetup c gc
 	gitConfigSpecialRemote u c' "hooktype" hooktype
@@ -129,7 +129,7 @@ store h = fileStorer $ \k src _p ->
 retrieve :: HookName -> Retriever
 retrieve h = fileRetriever $ \d k _p ->
 	unlessM (runHook h "retrieve" k (Just d) $ return True) $
-		error "failed to retrieve content"
+		giveup "failed to retrieve content"
 
 retrieveCheap :: HookName -> Key -> AssociatedFile -> FilePath -> Annex Bool
 retrieveCheap _ _ _ _ = return False
@@ -145,7 +145,7 @@ checkKey r h k = do
   where
 	action = "checkpresent"
 	findkey s = key2file k `elem` lines s
-	check Nothing = error $ action ++ " hook misconfigured"
+	check Nothing = giveup $ action ++ " hook misconfigured"
 	check (Just hook) = do
 		environ <- hookEnv action k Nothing
 		findkey <$> readProcessEnv "sh" ["-c", hook] environ