From: Joey Hess <joeyh@joeyh.name>
Date: Thu, 30 Jan 2025 20:51:42 +0000 (-0400)
Subject: fix truncateFilePath edge case on windows
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fix truncateFilePath edge case on windows

If the filepath starts with something that is not valid utf-8, it would
have returned "". And if the filepath was all non-valid utf-8, it would
also return "".
---

diff --git a/Utility/FileSystemEncoding.hs b/Utility/FileSystemEncoding.hs
index b4497f30af..cf9355ccd5 100644
--- a/Utility/FileSystemEncoding.hs
+++ b/Utility/FileSystemEncoding.hs
@@ -157,10 +157,13 @@ truncateFilePath n = toRawFilePath . reverse . go [] n
 	go coll cnt bs
 		| cnt <= 0 = coll
 		| otherwise = case S8.decode bs of
-			Just (c, x) | c /= S8.replacement_char ->
-				let x' = fromIntegral x
-				in if cnt - x' < 0
-					then coll
-					else go (c:coll) (cnt - x') (S8.drop 1 bs)
+			Just (c, x)
+				| c /= S8.replacement_char ->
+					let x' = fromIntegral x
+					in if cnt - x' < 0
+						then coll
+						else go (c:coll) (cnt - x') (S8.drop 1 bs)
+				| otherwise ->
+					go ('_':coll) (cnt - 1) (S8.drop 1 bs)
 			_ -> coll
 #endif