Remove ServiceBuilderCommand and implement the chain ops as standalone functions instead. (#6543)

* :)

* Slight tidy

* Remove ServiceBuilderCommand

* Remove whitespace

* Keep task manager alive for check_block/import_blocks

* Pass task_manager to run_until_exit

* Make task_manager in run_until_exit and make subcommands async

* Change the async_run fn to return a future and task manager

* async_run should take a result fn

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Fix spaces in export_raw_state

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/client/service/src/chain_ops/revert_chain.rs

@@ -0,0 +1,43 @@
+// Copyright 2017-2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::error::Error;
+use log::info;
+use sp_runtime::traits::{Block as BlockT, NumberFor, Zero};
+use sc_client_api::{Backend, UsageProvider};
+use std::sync::Arc;
+
+/// Performs a revert of `blocks` blocks.
+pub fn revert_chain<B, BA, C>(
+	client: Arc<C>,
+	backend: Arc<BA>,
+	blocks: NumberFor<B>
+) -> Result<(), Error>
+where
+	B: BlockT,
+	C: UsageProvider<B>,
+	BA: Backend<B>,
+{
+	let reverted = backend.revert(blocks, false)?;
+	let info = client.usage_info().chain;
+
+	if reverted.is_zero() {
+		info!("There aren't any non-finalized blocks to revert.");
+	} else {
+		info!("Reverted {} blocks. Best: #{} ({})", reverted, info.best_number, info.best_hash);
+	}
+	Ok(())
+}