Use VSCode-EmmyLua config to provide global config

In e356b99 ('Set up language server configuration automatically') logic
for setting up EmmyLuaLs automatically has been added. It used
a configuration file at the home directory.

It's not really very cool to spam with extension-specific files at the
user's home dir. A patch [^1] has been introduced allowing one to
specify a path to a global language server configuration file within the
VS Code options. Let's set up this instead.

[^1] EmmyLua/VSCode-EmmyLua#227

Author: georgiy-belyanin

src/extension.ts

@@ -1,7 +1,6 @@
 import * as vscode from 'vscode';
 import * as tt from './tt';
 import * as fs from 'fs';
-import * as os from 'os';
 import * as _ from 'lodash';
 import * as utils from './utils';
 
@@ -18,28 +17,28 @@ const emmyrc = {
 	}
 };
 const emmyrcFile = '.emmyrc.json';
+const globalEmmyrcKey = 'emmylua.misc.globalConfigPath';
+const globalEmmyrcPath = __dirname + '/emmyrc.json';
 
 async function initGlobalEmmyrc() {
-	const globalEmmyrcPath = `${os.homedir()}/${emmyrcFile}`;
+	const config = vscode.workspace.getConfiguration(undefined, null);
+	const configuredGlobalEmmyrcPath = config.get(globalEmmyrcKey);
 
-	if (!fs.existsSync(globalEmmyrcPath)) {
-		fs.writeFileSync(globalEmmyrcPath, JSON.stringify(emmyrc, undefined, 2));
-		vscode.window.showInformationMessage(`Initialized ${globalEmmyrcPath} with Tarantool-specific settings`);
-		return;
-	}
-
-	const f = fs.readFileSync(globalEmmyrcPath, 'utf8');
+	const f = fs.existsSync(globalEmmyrcPath) ? fs.readFileSync(globalEmmyrcPath, 'utf8') : '{}';
 	const existingEmmyrc = JSON.parse(f);
 	const upToDate = _.isMatch(existingEmmyrc, emmyrc);
-	if (upToDate) {
-		return;
+	if (!upToDate) {
+		fs.writeFileSync(globalEmmyrcPath, JSON.stringify(emmyrc, undefined, 2), { });
 	}
 
-	// TODO: Don't miss user-defined libraries.
-	const mergedEmmyrc = _.merge(existingEmmyrc, emmyrc);
+	const desiredGlobalEmmyrcPath = globalEmmyrcPath;
 
-	fs.writeFileSync(globalEmmyrcPath, JSON.stringify(mergedEmmyrc, undefined, 2));
-	vscode.window.showInformationMessage(`Updated existing ${globalEmmyrcPath} with actual Tarantool-specific configuration`);
+	if (configuredGlobalEmmyrcPath !== desiredGlobalEmmyrcPath) {
+		await config.update(globalEmmyrcKey, desiredGlobalEmmyrcPath, vscode.ConfigurationTarget.Global);
+		vscode.commands.executeCommand('emmy.restartServer');
+		vscode.window.showInformationMessage(`Updated EmmyLua extension with Tarantool-specific settings`);
+		return;
+	}
 }
 
 async function initVs() {