Add MoveNode::relative

ramen/src/command.rs

@@ -126,6 +126,7 @@ impl Command for DeleteNode {
 pub struct MoveNode {
     pub target: usize,
     pub to: glam::Vec2,
+    pub relative: bool,
 }
 
 impl Command for MoveNode {
@@ -135,6 +136,7 @@ impl Command for MoveNode {
         let undo = Self {
             target: self.target,
             to: target.pos,
+            relative: false,
         };
 
         Ok(Box::new(undo))
@@ -142,7 +144,13 @@ impl Command for MoveNode {
 
     fn apply(&self, graph: &mut Graph) -> GraphResult<()> {
         let target = graph.get_node_mut(self.target)?;
-        target.pos = self.to;
+        
+        if self.relative {
+            target.pos += self.to;
+        } else {
+            target.pos = self.to;
+        }
+
         Ok(())
     }
 }