unify exception handling into Utility.Exception

Removed old extensible-exceptions, only needed for very old ghc.

Made webdav use Utility.Exception, to work after some changes in DAV's
exception handling.

Removed Annex.Exception. Mostly this was trivial, but note that
tryAnnex is replaced with tryNonAsync and catchAnnex replaced with
catchNonAsync. In theory that could be a behavior change, since the former
caught all exceptions, and the latter don't catch async exceptions.

However, in practice, nothing in the Annex monad uses async exceptions.
Grepping for throwTo and killThread only find stuff in the assistant,
which does not seem related.

Command.Add.undo is changed to accept a SomeException, and things
that use it for rollback now catch non-async exceptions, rather than
only IOExceptions.

Remote/Helper/Chunked.hs

@@ -24,7 +24,6 @@ import Logs.Chunk
 import Utility.Metered
 import Crypto (EncKey)
 import Backend (isStableKey)
-import Annex.Exception
 
 import qualified Data.ByteString.Lazy as L
 import qualified Data.Map as M
@@ -172,7 +171,7 @@ seekResume h chunkkeys checker = do
 			liftIO $ hSeek h AbsoluteSeek sz
 			return (cks, toBytesProcessed sz)
 		| otherwise = do
-			v <- tryNonAsyncAnnex (checker k)
+			v <- tryNonAsync (checker k)
 			case v of
 				Right True ->
 					check pos' cks' sz
@@ -231,7 +230,7 @@ retrieveChunks retriever u chunkconfig encryptor basek dest basep sink
 		-- Optimisation: Try the unchunked key first, to avoid
 		-- looking in the git-annex branch for chunk counts
 		-- that are likely not there.
-		getunchunked `catchNonAsyncAnnex`
+		getunchunked `catchNonAsync`
 			const (go =<< chunkKeysOnly u basek)
 	| otherwise = go =<< chunkKeys u chunkconfig basek
   where
@@ -241,7 +240,7 @@ retrieveChunks retriever u chunkconfig encryptor basek dest basep sink
 		let ls' = maybe ls (setupResume ls) currsize
 		if any null ls'
 			then return True -- dest is already complete
-			else firstavail currsize ls' `catchNonAsyncAnnex` giveup
+			else firstavail currsize ls' `catchNonAsync` giveup
 
 	giveup e = do
 		warning (show e)
@@ -251,20 +250,20 @@ retrieveChunks retriever u chunkconfig encryptor basek dest basep sink
 	firstavail currsize ([]:ls) = firstavail currsize ls
 	firstavail currsize ((k:ks):ls)
 		| k == basek = getunchunked
-			`catchNonAsyncAnnex` (const $ firstavail currsize ls)
+			`catchNonAsync` (const $ firstavail currsize ls)
 		| otherwise = do
 			let offset = resumeOffset currsize k
 			let p = maybe basep
 				(offsetMeterUpdate basep . toBytesProcessed)
 				offset
-			v <- tryNonAsyncAnnex $
+			v <- tryNonAsync $
 				retriever (encryptor k) p $ \content ->
 					bracketIO (maybe opennew openresume offset) hClose $ \h -> do
 						void $ tosink (Just h) p content
 						let sz = toBytesProcessed $
 							fromMaybe 0 $ keyChunkSize k
 						getrest p h sz sz ks
-							`catchNonAsyncAnnex` giveup
+							`catchNonAsync` giveup
 			case v of
 				Left e
 					| null ls -> giveup e
@@ -372,7 +371,7 @@ checkPresentChunks checker u chunkconfig encryptor basek
 			Right False -> return $ Right False
 			Left e -> return $ Left $ show e
 
-	check = tryNonAsyncAnnex . checker . encryptor
+	check = tryNonAsync . checker . encryptor
 
 {- A key can be stored in a remote unchunked, or as a list of chunked keys.
  - This can be the case whether or not the remote is currently configured

Remote/Helper/Special.hs

@@ -42,13 +42,11 @@ import Remote.Helper.Chunked as X
 import Remote.Helper.Encryptable as X
 import Remote.Helper.Messages
 import Annex.Content
-import Annex.Exception
 import qualified Git
 import qualified Git.Command
 import qualified Git.Construct
 
 import qualified Data.ByteString.Lazy as L
-import Control.Exception (bracket)
 import qualified Data.Map as M
 
 {- Special remotes don't have a configured url, so Git.Repo does not
@@ -174,7 +172,7 @@ specialRemote' cfg c preparestorer prepareretriever prepareremover preparecheckp
 	cip = cipherKey c
 	gpgopts = getGpgEncParams encr
 
-	safely a = catchNonAsyncAnnex a (\e -> warning (show e) >> return False)
+	safely a = catchNonAsync a (\e -> warning (show e) >> return False)
 
 	-- chunk, then encrypt, then feed to the storer
 	storeKeyGen k p enc = safely $ preparestorer k $ safely . go