feat: add --fork-block-number setter for anvil bindings (#1468)

ethers-core/src/utils/anvil.rs

@@ -82,6 +82,7 @@ pub struct Anvil {
     block_time: Option<u64>,
     mnemonic: Option<String>,
     fork: Option<String>,
+    fork_block_number: Option<u64>,
     args: Vec<String>,
 }
 
@@ -113,6 +114,15 @@ impl Anvil {
         self
     }
 
+    /// Sets the `fork-block-number` which will be used in addition to [`Self::fork`].
+    ///
+    /// **Note:** if set, then this requires `fork` to be set as well
+    #[must_use]
+    pub fn fork_block_number<T: Into<u64>>(mut self, fork_block_number: T) -> Self {
+        self.fork_block_number = Some(fork_block_number.into());
+        self
+    }
+
     /// Sets the `fork` argument to fork from another currently running Ethereum client
     /// at a given block. Input should be the HTTP location and port of the other client,
     /// e.g. `http://localhost:8545`. You can optionally specify the block to fork from
@@ -163,6 +173,10 @@ impl Anvil {
             cmd.arg("-f").arg(fork);
         }
 
+        if let Some(fork_block_number) = self.fork_block_number {
+            cmd.arg("--fork-block-number").arg(fork_block_number.to_string());
+        }
+
         cmd.args(self.args);
 
         let mut child = cmd.spawn().expect("couldnt start anvil");