Setup pre-commit lint hook

Squashed commit of the following:

commit 02591b74c184faf7f7156e95cf05a78fb0ea22a7
Merge: 4057c8ae a32c1f2e
Author: ArtemBaskal <a.baskal@adguard.com>
Date:   Wed Jul 15 12:36:20 2020 +0300

    Merge branch 'master' into feature/git-hooks

commit 4057c8ae117dfb5de493769dbf1577c8d59035a4
Author: ArtemBaskal <a.baskal@adguard.com>
Date:   Tue Jul 14 20:04:38 2020 +0300

    Review changes

commit 2400ab77d9e0e3f7b62b0ffd64aeccf369ff84cd
Author: ArtemBaskal <a.baskal@adguard.com>
Date:   Tue Jul 14 16:27:14 2020 +0300

    Add lint-js and lint-go to .PHONY

commit 8a4efc2cb4f2d53ebea4b88b8182e4c1eb7812eb
Author: ArtemBaskal <a.baskal@adguard.com>
Date:   Tue Jul 14 15:47:14 2020 +0300

    Run linter only if corresponding file extension is changed

commit 8e2e110e9c9c3f865503cf3c0cd3e31dd4579b71
Author: ArtemBaskal <a.baskal@adguard.com>
Date:   Mon Jul 13 19:07:42 2020 +0300

    Setup pre-commit lint hooks

.githooks/pre-commit

@@ -0,0 +1,12 @@
+#!/bin/bash
+set -e;
+git diff --cached --name-only | grep -q '.js$' && make lint-js;
+
+found=0
+git diff --cached --name-only | grep -q '.go$' && found=1
+if [ $found == 1 ]; then
+	make lint-go || exit 1
+	go test ./... || exit 1
+fi
+
+exit 0;

Makefile

@@ -88,9 +88,12 @@ ifndef DOCKER_IMAGE_NAME
 $(error DOCKER_IMAGE_NAME value is not set)
 endif
 
-.PHONY: all build client client-watch docker lint test dependencies clean release docker-multi-arch
+.PHONY: all build client client-watch docker lint lint-js lint-go test dependencies clean release docker-multi-arch
 all: build
 
+init:
+	git config core.hooksPath .githooks
+
 build: dependencies client
 	PATH=$(GOPATH)/bin:$(PATH) go generate ./...
 	CGO_ENABLED=0 go build -ldflags="-s -w -X main.version=$(VERSION) -X main.channel=$(CHANNEL) -X main.goarm=$(GOARM)"
@@ -116,11 +119,16 @@ docker:
 	@echo Now you can run the docker image:
 	@echo docker run --name "adguard-home" -p 53:53/tcp -p 53:53/udp -p 80:80/tcp -p 443:443/tcp -p 853:853/tcp -p 3000:3000/tcp $(DOCKER_IMAGE_NAME)
 
-lint:
-	@echo Running linters
-	golangci-lint run ./...
+lint: lint-js lint-go
+
+lint-js:
+	@echo Running js linter
 	npm --prefix client run lint
 
+lint-go:
+	@echo Running go linter
+	golangci-lint run
+
 test:
 	@echo Running unit-tests
 	go test -race -v -bench=. -coverprofile=coverage.txt -covermode=atomic ./...
@@ -223,4 +231,4 @@ define write_version_file
 
 	# Finish
 	echo "}" >> $(DIST_DIR)/version.json
-endef
+endef

README.md

@@ -150,11 +150,14 @@ Is there a chance to handle this in the future? DNS will never be enough to do t
 
 ### Prerequisites
 
+Run `make init` to prepare the development environment.
+
 You will need this to build AdGuard Home:
 
  * [go](https://golang.org/dl/) v1.14 or later.
  * [node.js](https://nodejs.org/en/download/) v10 or later.
-
+ * [golangci-lint](https://github.com/golangci/golangci-lint)
+ 
 ### Building
 
 Open Terminal and execute these commands: