Allow for customizable recent genesis window

beacon_node/client/src/config.rs

@@ -42,7 +42,10 @@ pub enum BeaconChainStartMethod {
     /// Create a new beacon chain that can connect to mainnet.
     ///
     /// Set the genesis time to be the start of the previous 30-minute window.
-    RecentGenesis { validator_count: usize },
+    RecentGenesis {
+        validator_count: usize,
+        minutes: u64,
+    },
     /// Create a new beacon chain with `genesis_time` and `validator_count` validators, all with well-known
     /// secret keys.
     Generated {

beacon_node/client/src/lib.rs

@@ -88,9 +88,15 @@ where
                 crit!(log, "No mainnet beacon chain startup specification.");
                 return Err("Mainnet is not yet specified. We're working on it.".into());
             }
-            BeaconChainStartMethod::RecentGenesis { validator_count } => {
-                BeaconChainBuilder::recent_genesis(*validator_count, spec.clone(), log.clone())
-            }
+            BeaconChainStartMethod::RecentGenesis {
+                validator_count,
+                minutes,
+            } => BeaconChainBuilder::recent_genesis(
+                *validator_count,
+                *minutes,
+                spec.clone(),
+                log.clone(),
+            ),
             BeaconChainStartMethod::Generated {
                 validator_count,
                 genesis_time,