mount: fix exit code on cancellation

cmd/restic/cmd_mount.go

@@ -190,7 +190,7 @@ func runMount(ctx context.Context, opts MountOptions, gopts GlobalOptions, args
 			Warnf("unable to umount (maybe already umounted or still in use?): %v\n", err)
 		}
 
-		return nil
+		return ErrOK
 	case <-done:
 		// clean shutdown, nothing to do
 	}

cmd/restic/main.go

@@ -25,6 +25,8 @@ func init() {
 	_, _ = maxprocs.Set()
 }
 
+var ErrOK = errors.New("ok")
+
 // cmdRoot is the base command when no other command has been specified.
 var cmdRoot = &cobra.Command{
 	Use:   "restic",
@@ -125,6 +127,9 @@ func main() {
 
 	if err == nil {
 		err = ctx.Err()
+	} else if err == ErrOK {
+		// ErrOK overwrites context cancelation errors
+		err = nil
 	}
 
 	switch {