hst/fsbind: optional autoetc behaviour

This generalises the special field allowing any special behaviour to be matched from target.

Signed-off-by: Ophestra <cat@gensokyo.uk>

hst/fs.go

@@ -18,11 +18,19 @@ type FilesystemConfig interface {
 	// Host returns a slice of all host paths used by this operation.
 	Host() []*container.Absolute
 	// Apply appends the [container.Op] implementing this operation.
-	Apply(ops *container.Ops)
+	Apply(z *ApplyState)
 
 	fmt.Stringer
 }
 
+// ApplyState holds the address of [container.Ops] and any relevant application state.
+type ApplyState struct {
+	// AutoEtcPrefix is the prefix for [container.AutoEtcOp].
+	AutoEtcPrefix string
+
+	*container.Ops
+}
+
 var (
 	ErrFSNull = errors.New("unexpected null in mount point")
 )