Add "new-testnet" command to lcli (#853)

* Add new command to lcli

* Add lcli to dockerfile

* Add min validator count param

* Fix bug in arg parsing

* Fix 0x address prefix issue

* Add effective balance increment

* Add ejection balance

* Fix PR comments

lcli/src/new_testnet.rs

@@ -0,0 +1,59 @@
+use crate::helpers::*;
+use clap::ArgMatches;
+use eth2_testnet_config::Eth2TestnetConfig;
+use std::path::PathBuf;
+use types::{EthSpec, YamlConfig};
+
+pub fn run<T: EthSpec>(matches: &ArgMatches) -> Result<(), String> {
+    let testnet_dir_path = parse_path_with_default_in_home_dir(
+        matches,
+        "testnet-dir",
+        PathBuf::from(".lighthouse/testnet"),
+    )?;
+    let min_genesis_time = parse_u64_opt(matches, "min-genesis-time")?;
+    let min_genesis_delay = parse_u64(matches, "min-genesis-delay")?;
+    let min_genesis_active_validator_count =
+        parse_u64(matches, "min-genesis-active-validator-count")?;
+    let min_deposit_amount = parse_u64(matches, "min-deposit-amount")?;
+    let max_effective_balance = parse_u64(matches, "max-effective-balance")?;
+    let effective_balance_increment = parse_u64(matches, "effective-balance-increment")?;
+    let ejection_balance = parse_u64(matches, "ejection-balance")?;
+    let eth1_follow_distance = parse_u64(matches, "eth1-follow-distance")?;
+    let deposit_contract_deploy_block = parse_u64(matches, "deposit-contract-deploy-block")?;
+    let genesis_fork_version = parse_fork_opt(matches, "genesis-fork-version")?;
+    let deposit_contract_address = parse_address(matches, "deposit-contract-address")?;
+
+    if testnet_dir_path.exists() {
+        return Err(format!(
+            "{:?} already exists, will not overwrite",
+            testnet_dir_path
+        ));
+    }
+
+    let mut spec = T::default_spec();
+    if let Some(time) = min_genesis_time {
+        spec.min_genesis_time = time;
+    } else {
+        spec.min_genesis_time = time_now()?;
+    }
+    spec.min_deposit_amount = min_deposit_amount;
+    spec.min_genesis_active_validator_count = min_genesis_active_validator_count;
+    spec.max_effective_balance = max_effective_balance;
+    spec.effective_balance_increment = effective_balance_increment;
+    spec.ejection_balance = ejection_balance;
+    spec.eth1_follow_distance = eth1_follow_distance;
+    spec.min_genesis_delay = min_genesis_delay;
+    if let Some(v) = genesis_fork_version {
+        spec.genesis_fork_version = v;
+    }
+
+    let testnet: Eth2TestnetConfig<T> = Eth2TestnetConfig {
+        deposit_contract_address: format!("{:?}", deposit_contract_address),
+        deposit_contract_deploy_block,
+        boot_enr: Some(vec![]),
+        genesis_state: None,
+        yaml_config: Some(YamlConfig::from_spec::<T>(&spec)),
+    };
+
+    testnet.write_to_file(testnet_dir_path)
+}