Drop and warn about non-normalized file names on Linux/Windows (fixes #329)

scanner/walk.go

@@ -13,6 +13,7 @@ import (
 	"runtime"
 	"strings"
 	"time"
+	"code.google.com/p/go.text/unicode/norm"
 
 	"github.com/calmh/syncthing/lamport"
 	"github.com/calmh/syncthing/protocol"
@@ -159,6 +160,11 @@ func (w *Walker) walkAndHashFiles(res *[]File, ign map[string][]string) filepath
 			return nil
 		}
 
+		if (runtime.GOOS == "linux" || runtime.GOOS == "windows") && !norm.NFC.IsNormalString(rn) {
+			l.Warnf("File %q contains non-NFC UTF-8 sequences and cannot be synced. Consider renaming.", rn)
+			return nil
+		}
+
 		if info.Mode().IsDir() {
 			if w.CurrentFiler != nil {
 				cf := w.CurrentFiler.CurrentFile(rn)