packer.json

{
  "variables": {
    "name": "nginx-ssl-proxy",
    "git_commit": "",
    "git_branch": "",
    "account_file": "",
    "project_id": "null"
  },
  "builders": [
    {
      "type": "docker",
      "image": "nginx",
      "commit": "true" 
    }
  ],
  "provisioners": [
    {
      "type": "shell",
      "inline": [
        "rm /etc/nginx/conf.d/*.conf"
      ]
    },
    {
      "type": "file",
      "source": "nginx/nginx.conf",
      "destination": "/etc/nginx/nginx.conf"
    },
    {
      "type": "file",
      "source": "nginx/proxy_ssl.conf",
      "destination": "/usr/src/proxy_ssl.conf"
    },
    {
      "type": "file",
      "source": "nginx/proxy_nossl.conf",
      "destination": "/usr/src/proxy_nossl.conf"
    },
    {
      "type": "file",
      "source": "start.sh",
      "destination": "/usr/bin/start.sh"
    }
  ],
  "post-processors": [
    [
        {
            "type": "docker-tag",
            "repository": "gcr.io/{{user `project_id`}}/{{user `name`}}",
            "tag": "{{user `git_branch`}}-{{user `git_commit`}}",
            "only": ["docker"]
        }
    ]
  ]
}