filter out control characters in error messages

giveup changed to filter out control characters. (It is too low level to
make it use StringContainingQuotedPath.)

error still does not, but it should only be used for internal errors,
where the message is not attacker-controlled.

Changed a lot of existing error to giveup when it is not strictly an
internal error.

Of course, other exceptions can still be thrown, either by code in
git-annex, or a library, that include some attacker-controlled value.
This does not guard against those.

Sponsored-by: Noam Kremen on Patreon

Git/UnionMerge.hs

@@ -78,7 +78,7 @@ doMerge hashhandle ch differ repo streamer = do
 	go [] = noop
 	go (info:file:rest) = mergeFile info file hashhandle ch >>=
 		maybe (go rest) (\l -> streamer l >> go rest)
-	go (_:[]) = error $ "parse error " ++ show differ
+	go (_:[]) = giveup $ "parse error " ++ show differ
 
 {- Given an info line from a git raw diff, and the filename, generates
  - a line suitable for update-index that union merges the two sides of the