[perft] Print the fen string of the board position

perft/src/main.rs

@@ -1,4 +1,7 @@
-use chessfriend_position::{Position, fen::FromFenStr, perft::Perft};
+use chessfriend_position::{
+    Position,
+    fen::{FromFenStr, ToFenStr},
+};
 use clap::Parser;
 
 #[derive(Parser, Debug)]
@@ -14,14 +17,15 @@ fn main() -> anyhow::Result<()> {
     let args = Arguments::parse();
     let depth = args.depth;
 
-    println!("depth {depth}");
-
     let mut position = if let Some(fen) = args.fen {
         Position::from_fen_str(&fen)?
     } else {
         Position::starting(None)
     };
 
+    println!("fen \"{}\"", position.to_fen_str().unwrap());
+    println!("depth {depth}");
+
     let nodes_searched = position.perft(depth);
 
     println!("nodes {nodes_searched}");