Fix CLI setup again (#4851)

* Fix CLI setup again

We need to set `config_dir` and `database_path` for almost every
command.
This fixes `purge-chain` and also adds a test to make sure we don't
break it again.

* Adds missing test files

* Split methods

substrate/bin/node/cli/tests/common.rs

@@ -0,0 +1,34 @@
+// Copyright 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 std::{process::{Child, ExitStatus}, thread, time::Duration};
+
+/// Wait for the given `child` the given ammount of `secs`.
+///
+/// Returns the `Some(exit status)` or `None` if the process did not finish in the given time.
+pub fn wait_for(child: &mut Child, secs: usize) -> Option<ExitStatus> {
+	for _ in 0..secs {
+		match child.try_wait().unwrap() {
+			Some(status) => return Some(status),
+			None => thread::sleep(Duration::from_secs(1)),
+		}
+	}
+	eprintln!("Took to long to exit. Killing...");
+	let _ = child.kill();
+	child.wait().unwrap();
+
+	None
+}