convert to withCreateProcess for async exception safety

This handles all sites where checkSuccessProcess/ignoreFailureProcess
is used, except for one: Git.Command.pipeReadLazy
That one will be significantly more work to convert to bracketing.

(Also skipped Command.Assistant.autoStart, but it does not need to
shut down the processes it started on exception because they are
git-annex assistant daemons..)

forceSuccessProcess is done, except for createProcessSuccess.
All call sites of createProcessSuccess will need to be converted
to bracketing.

(process pools still todo also)

Git/CatFile.hs

@@ -180,14 +180,16 @@ querySingle o r repo reader = assertLocal repo $
 			, std_in = Inherit
 			, std_out = CreatePipe
 			}
-		pid <- createProcess p'
-		let h = stdoutHandle pid
-		output <- reader h
-		hClose h
-		ifM (checkSuccessProcess (processHandle pid))
+		withCreateProcess p' go
+  where
+	go _ (Just outh) _ pid = do
+		output <- reader outh
+		hClose outh
+		ifM (checkSuccessProcess pid)
 			( return (Just output)
 			, return Nothing
 			)
+	go _ _ _ _ = error "internal"
 
 querySize :: Ref -> Repo -> IO (Maybe FileSize)
 querySize r repo = maybe Nothing (readMaybe . takeWhile (/= '\n'))