Fix docker-compose.yml, Add more Makefile targets

Makefile

@@ -6,5 +6,11 @@ stop:
 	@docker-compose -p janus down
 stop-clean-data:
 	@docker-compose -p janus down -v
+copy-jobs:
+	@docker cp jenkins:/var/jenkins_home/jobs/. ./jenkins/jobs
+update-plugins:
+	@docker exec -it jenkins ls /var/jenkins_home/plugins/ | grep -v jpi > ./jenkins/plugins.txt
+print-ssh-key:
+	@docker exec -it jenkins cat "/home/jenkins/.ssh/gitlab-ssh.pub"
 clean-images:
 	@docker rmi `docker images -q -f "dangling=true"`

docker-compose.yml

@@ -58,7 +58,8 @@ services:
   # https://jenkins.io/doc/book/blueocean/
   jenkins:
     build:
-      dockerfile: ./jenkins
+      dockerfile: ./jenkins/Dockerfile
+      context: ./jenkins
       args:
         HOST_DOCKER_VERSION: ${HOST_DOCKER_VERSION:-19.03.5}
     container_name: jenkins