vfs: fix cache encoding with special characters - #7760

The vfs use the hardcoded OS encoding when creating temp file,
but decode it with encoding for the local filesystem (--local-encoding)
when copying it to remote.
This caused failures when the filenames contained special characters.
The hardcoded OS encoding is now used uniformly.

lib/encoder/internal/gen/main.go

@@ -229,8 +229,8 @@ func main() {
 			fatalW(fd.WriteString(" "))("Write:")
 		}
 		in, out := buildTestString(
-			[]mapping{getMapping(m.mask)},                               // pick
-			[]mapping{getMapping(encoder.EncodeZero)},                   // quote
+			[]mapping{getMapping(m.mask)},             // pick
+			[]mapping{getMapping(encoder.EncodeZero)}, // quote
 			printables, fullwidthPrintables, encodables, encoded, greek) // fill
 		fatalW(fmt.Fprintf(fd, `{ // %d
 		mask: %s,

vfs/vfscache/cache.go

@@ -212,7 +212,7 @@ func (c *Cache) createItemDir(name string) (string, error) {
 
 // getBackend gets a backend for a cache root dir
 func getBackend(ctx context.Context, parentPath string, name string, relativeDirPath string) (fs.Fs, error) {
-	path := fmt.Sprintf("%s/%s/%s", parentPath, name, relativeDirPath)
+	path := fmt.Sprintf(":local,encoding='%v':%s/%s/%s", encoder.OS, parentPath, name, relativeDirPath)
 	return fscache.Get(ctx, path)
 }