fix mojibake reversion in display of utf8

When displaying a ByteString like "💕", safeOutput operates on
individual bytes like "\240\159\146\149" and isControl '\146' = True,
so it got truncated to just "\240".

So, only treat the low control characters, and DEL, as control
characters.

Also split Utility.Terminal out of Utility.SafeOutput. The latter needs
win32, but Utility.SafeOutput is used by Control.Exception, which is
used by Setup.

Sponsored-by: Nicholas Golder-Manning on Patreon

Annex/UntrustedFilePath.hs

@@ -10,6 +10,8 @@ module Annex.UntrustedFilePath where
 import Data.Char
 import System.FilePath
 
+import Utility.SafeOutput
+
 {- Given a string that we'd like to use as the basis for FilePath, but that
  - was provided by a third party and is not to be trusted, returns the closest
  - sane FilePath.
@@ -55,10 +57,7 @@ sanitizeLeadingFilePathCharacter s = s
 controlCharacterInFilePath :: FilePath -> Bool
 controlCharacterInFilePath = any (not . safechar)
   where
-	safechar c
-		| not (isControl c) = True
-		| c == '\t' = True
-		| otherwise = False
+	safechar c = safeOutputChar c && c /= '\n'
 
 {- ../ is a path traversal, no matter where it appears.
  -

Command/ExamineKey.hs

@@ -16,7 +16,7 @@ import Annex.Link
 import Backend
 import Types.Backend
 import Types.Key
-import Utility.SafeOutput
+import Utility.Terminal
 
 import Data.Char
 import qualified Data.ByteString as B

Command/Find.hs

@@ -19,7 +19,7 @@ import Types.Key
 import Git.FilePath
 import qualified Utility.Format
 import Utility.DataUnits
-import Utility.SafeOutput
+import Utility.Terminal
 
 cmd :: Command
 cmd = withAnnexOptions [annexedMatchingOptions] $ mkCommand $

Command/FindKeys.hs

@@ -10,7 +10,7 @@ module Command.FindKeys where
 import Command
 import qualified Command.Find
 import qualified Utility.Format
-import Utility.SafeOutput
+import Utility.Terminal
 
 cmd :: Command
 cmd = withAnnexOptions [keyMatchingOptions] $ Command.Find.mkCommand $

Utility/SafeOutput.hs

@@ -11,55 +11,27 @@
 
 module Utility.SafeOutput (
 	safeOutput,
-	IsTerminal(..),
-	checkIsTerminal,
+	safeOutputChar,
 ) where
 
 import Data.Char
 import qualified Data.ByteString as S
 import System.IO
-#ifdef mingw32_HOST_OS
-import System.Win32.MinTTY (isMinTTYHandle)
-import System.Win32.File
-import System.Win32.Types
-import Graphics.Win32.Misc
-import Control.Exception
-#endif
 
 class SafeOutputtable t where
 	safeOutput :: t -> t
 
 instance SafeOutputtable String where
-	safeOutput = filter safeChar
+	safeOutput = filter safeOutputChar
 
 instance SafeOutputtable S.ByteString where
-	safeOutput = S.filter (safeChar . chr . fromIntegral)
+	safeOutput = S.filter (safeOutputChar . chr . fromIntegral)
 
-safeChar :: Char -> Bool
-safeChar c
+safeOutputChar :: Char -> Bool
+safeOutputChar c
 	| not (isControl c) = True
 	| c == '\n' = True
 	| c == '\t' = True
+	| c == '\DEL' = False
+	| ord c > 31 = True
 	| otherwise = False
-
-newtype IsTerminal = IsTerminal Bool
-
-checkIsTerminal :: Handle -> IO IsTerminal
-checkIsTerminal h = do
-#ifndef mingw32_HOST_OS
-	b <- hIsTerminalDevice h
-	return (IsTerminal b)
-#else
-	b <- hIsTerminalDevice h
-	if b
-		then return (IsTerminal b)
-		else do
-			h' <- getStdHandle sTD_OUTPUT_HANDLE
-				`catch` \(_ :: IOError) ->
-					return nullHANDLE
-			if h == nullHANDLE
-				then return (IsTerminal False)
-				else do
-					b' <- isMinTTYHandle h'
-					return (IsTerminal b)
-#endif

Utility/Terminal.hs

@@ -0,0 +1,47 @@
+{- Determining if output is to a terminal.
+ -
+ - Copyright 2023 Joey Hess <id@joeyh.name>
+ -
+ - License: BSD-2-clause
+ -}
+
+{-# LANGUAGE CPP #-}
+{-# OPTIONS_GHC -fno-warn-tabs #-}
+
+module Utility.Terminal (
+	IsTerminal(..),
+	checkIsTerminal,
+) where
+
+import Data.Char
+import qualified Data.ByteString as S
+import System.IO
+#ifdef mingw32_HOST_OS
+import System.Win32.MinTTY (isMinTTYHandle)
+import System.Win32.File
+import System.Win32.Types
+import Graphics.Win32.Misc
+import Control.Exception
+#endif
+
+newtype IsTerminal = IsTerminal Bool
+
+checkIsTerminal :: Handle -> IO IsTerminal
+checkIsTerminal h = do
+#ifndef mingw32_HOST_OS
+	b <- hIsTerminalDevice h
+	return (IsTerminal b)
+#else
+	b <- hIsTerminalDevice h
+	if b
+		then return (IsTerminal b)
+		else do
+			h' <- getStdHandle sTD_OUTPUT_HANDLE
+				`catch` \(_ :: IOError) ->
+					return nullHANDLE
+			if h == nullHANDLE
+				then return (IsTerminal False)
+				else do
+					b' <- isMinTTYHandle h'
+					return (IsTerminal b)
+#endif

git-annex.cabal

@@ -1144,6 +1144,7 @@ Executable git-annex
     Utility.SshHost
     Utility.Su
     Utility.SystemDirectory
+    Utility.Terminal
     Utility.TimeStamp
     Utility.TList
     Utility.Tense