fix #1970 - add support for RESTORE (#2535)

* - Added RESTORE functionality

* add FIRST_KEY_INDEX, fix tests, clean example, add example to examples table

* use returnBuffers in test

---------

Co-authored-by: Leibale Eidelman <me@leibale.com>

packages/client/lib/commands/RESTORE.spec.ts

@@ -0,0 +1,74 @@
+import { strict as assert } from 'assert';
+import testUtils, { GLOBAL } from '../test-utils';
+import { transformArguments } from './RESTORE';
+
+describe('RESTORE', () => {
+    describe('transformArguments', () => {
+        it('simple', () => {
+            assert.deepEqual(
+                transformArguments('key', 0, 'value'),
+                ['RESTORE', 'key', '0', 'value']
+            );
+        });
+
+        it('with REPLACE', () => {
+            assert.deepEqual(
+                transformArguments('key', 0, 'value', {
+                    REPLACE: true
+                }),
+                ['RESTORE', 'key', '0', 'value', 'REPLACE']
+            );
+        });
+
+        it('with ABSTTL', () => {
+            assert.deepEqual(
+                transformArguments('key', 0, 'value', {
+                    ABSTTL: true
+                }),
+                ['RESTORE', 'key', '0', 'value', 'ABSTTL']
+            );
+        });
+
+        it('with IDLETIME', () => {
+            assert.deepEqual(
+                transformArguments('key', 0, 'value', {
+                    IDLETIME: 1
+                }),
+                ['RESTORE', 'key', '0', 'value', 'IDLETIME', '1']
+            );
+        });
+
+        it('with FREQ', () => {
+            assert.deepEqual(
+                transformArguments('key', 0, 'value', {
+                    FREQ: 1
+                }),
+                ['RESTORE', 'key', '0', 'value', 'FREQ', '1']
+            );
+        });
+
+        it('with REPLACE, ABSTTL, IDLETIME and FREQ', () => {
+            assert.deepEqual(
+                transformArguments('key', 0, 'value', {
+                    REPLACE: true,
+                    ABSTTL: true,
+                    IDLETIME: 1,
+                    FREQ: 2
+                }),
+                ['RESTORE', 'key', '0', 'value', 'REPLACE', 'ABSTTL', 'IDLETIME', '1', 'FREQ', '2']
+            );
+        });
+    });
+
+    testUtils.testWithClient('client.restore', async client => {
+        const [, dump] = await Promise.all([
+            client.set('source', 'value'),
+            client.dump(client.commandOptions({ returnBuffers: true }), 'source')
+        ]);
+
+        assert.equal(
+            await client.restore('destination', 0, dump),
+            'OK'
+        );
+    }, GLOBAL.SERVERS.OPEN);
+});