full emulation of git filename escaping

Not yet used, but the plan is to make git-annex use this when displaying
filenames similar to how git does.

Sponsored-by: Lawrence Brogan on Patreon

Git/Filename.hs

@@ -11,7 +11,7 @@
 module Git.Filename where
 
 import Common
-import Utility.Format (decode_c, encode_c, isUtf8Byte)
+import Utility.Format (decode_c, encode_c, encode_c', isUtf8Byte)
 import Utility.QuickCheck
 
 import Data.Char
@@ -39,6 +39,20 @@ encodeAlways s = "\"" <> encode_c needencode s <> "\""
   where
 	needencode c = isUtf8Byte c || c == fromIntegral (ord '"')
 
+-- git config core.quotePath controls whether to quote unicode characters
+newtype QuotePath = QuotePath Bool
+
+-- encodes and double quotes when git would
+encode :: QuotePath -> RawFilePath -> S.ByteString
+encode (QuotePath qp) s = case encode_c' needencode s of
+	Nothing -> s
+	Just s' -> "\"" <> s' <> "\""
+  where
+	needencode c
+		| c == fromIntegral (ord '"') = True
+		| qp = isUtf8Byte c
+		| otherwise = False
+
 -- Encoding and then decoding roundtrips only when the string does not
 -- contain high unicode, because eg, both "\12345" and "\227\128\185"
 -- are encoded to "\343\200\271".

doc/todo/terminal_escapes_in_filenames.mdwn

@@ -35,3 +35,8 @@ useful defense in depth against terminal security holes, and also good to
 behave more like git.
 
 --[[Joey]]
+
+> Git.Filename.encode is implemented, and only needs to be used.
+> Note that core.quotePath controls whether git quotes unicode characters
+> (by default it does), so once this gets implemented, some users may want
+> to set that config to false. --[[Joey]]