add cli for purge chain (#609)

substrate/substrate/cli/src/cli.yml

@@ -211,3 +211,17 @@ subcommands:
               value_name: PATH
               help: Specify custom base path.
               takes_value: true
+  - purge-chain:
+      about: Remove the whole chain data.
+      args:
+          - chain:
+              long: chain
+              value_name: CHAIN_SPEC
+              help: Specify the chain specification.
+              takes_value: true
+          - base-path:
+              long: base-path
+              short: d
+              value_name: PATH
+              help: Specify custom base path.
+              takes_value: true

substrate/substrate/cli/src/lib.rs

@@ -65,6 +65,7 @@ use network::NonReservedPeerMode;
 
 use std::io::{Write, Read, stdin, stdout};
 use std::iter;
+use std::fs;
 use std::fs::File;
 use std::net::{Ipv4Addr, SocketAddr};
 use std::path::{Path, PathBuf};
@@ -213,6 +214,12 @@ where
 		return Ok(Action::ExecutedInternally);
 	}
 
+	if let Some(matches) = matches.subcommand_matches("purge-chain") {
+		let spec = load_spec(&matches, spec_factory)?;
+		purge_chain::<F>(matches, spec)?;
+		return Ok(Action::ExecutedInternally);
+	}
+
 	let spec = load_spec(&matches, spec_factory)?;
 	let mut config = service::Configuration::default_with_spec(spec);
 
@@ -417,6 +424,30 @@ fn revert_chain<F>(matches: &clap::ArgMatches, spec: ChainSpec<FactoryGenesis<F>
 	Ok(service::chain_ops::revert_chain::<F>(config, As::sa(blocks))?)
 }
 
+fn purge_chain<F>(matches: &clap::ArgMatches, spec: ChainSpec<FactoryGenesis<F>>) -> error::Result<()>
+	where F: ServiceFactory,
+{
+	let base_path = base_path(matches);
+	let database_path = db_path(&base_path, spec.id());
+
+	print!("Are you sure to remove {:?}? (y/n)", &database_path);
+	stdout().flush().expect("failed to flush stdout");
+
+	let mut input = String::new();
+	stdin().read_line(&mut input)?;
+	let input = input.trim();
+
+	match input.chars().nth(0) {
+		Some('y') | Some('Y') => {
+			fs::remove_dir_all(&database_path)?;
+			println!("{:?} removed.", &database_path);
+		},
+		_ => println!("Aborted"),
+	}
+
+	Ok(())
+}
+
 fn parse_address(default: &str, port_param: &str, matches: &clap::ArgMatches) -> Result<SocketAddr, String> {
 	let mut address: SocketAddr = default.parse().ok().ok_or_else(|| format!("Invalid address specified for --{}.", port_param))?;
 	if let Some(port) = matches.value_of(port_param) {