Resolve "Populate README.md of docker_build job"

# 🐳 Docker

🚧 *Work in progress*

## Description

Build a [docker](https://www.docker.com/) image of your application

from a Dockerfile at the root of your project, and push it to a

remote registry. The build part is done using

[kaniko](https://github.com/GoogleContainerTools/kaniko).

!!! info

    By default, your images will be pushed to the Gitlab Container

    Registry of your Gitlab instance.

## How to use it

1. Create a

   [Dockerfile](https://docs.docker.com/get-started/part2/#sample-dockerfile) (by default at the root of your project)

   to containerize your application

2. Choose a version in [version list](#versions)

3. Add the corresponding URL to your `.gitlab-ci.yml` file (see [Getting

   started](/getting-started)). Example:

    ```yaml

    include:

      - remote: 'https://jobs.go2scale.io/docker_build.yml'

    ```

4. If you need to customize the job (stage, variables, ...) 👉 check the [jobs

   customization](/getting-started/#jobs-customization)

5. Well done, your job is ready to work ! 😀

## Job details

* Job name: `docker_build`

* Docker image: [`gcr.io/kaniko-project/executor:debug-v0.20.0`](https://github.com/GoogleContainerTools/kaniko)

* Default stage: `build`

### Build behavior

!!! info

    This build will use Gitlab CI predefined [environment variables]

    (https://docs.gitlab.com/ee/ci/variables/predefined_variables.html)

    to know you are in a `commit` context or a `tag` context

    (for example if you are releasing a new version of your project).

The registry and tag of the resulting Docker image follow this behavior:

| `CUSTOM_REGISTRY` used ? <img width=10/> | `CUSTOM_TAG` used ? | Are you pushing git tag ? | Registry where image is pushed | Docker tag applied to the image |

|:-|:-|:-|:-|:-

| No  | No  | No  | Gitlab project registry | Last commit SHA |

| No  | No  | Yes | Gitlab project registry | Git tag name    |

| No  | Yes | No  | Gitlab project registry | `CUSTOM_TAG`    |

| No  | Yes | Yes | Gitlab project registry | `CUSTOM_TAG`    |

| Yes | No  | No  | `CUSTOM_REGISTRY`       | Last commit SHA |

| Yes | No  | Yes | `CUSTOM_REGISTRY`       | Git tag name    |

| Yes | Yes | No  | `CUSTOM_REGISTRY`       | `CUSTOM_TAG`    |

| Yes | Yes | Yes | `CUSTOM_REGISTRY`       | `CUSTOM_TAG`    |

### Variables

| VARIABLE NAME | DESCRIPTION | DEFAULT VALUE |

|:-|:-|:-

| `CUSTOM_REGISTRY` <img width=100/> | If you want to use another registry than the Gitlab one | ` ` |

| `REGISTRY_USER` | To authenticate with the `CUSTOM_REGISTRY` | ` ` |

| `REGISTRY_PASSWORD` | To authenticate with the `CUSTOM_REGISTRY` | ` ` |

| `CUSTOM_TAG` | If you want a specific tag for your image | ` ` |

| `COMMIT_CREATE_LATEST` | In a commit context, also update `latest` tag | `false` |

| `TAG_CREATE_LATEST` | In a tag context, also update `latest` tag | `true` |

| `DOCKERFILE_PATH` | Path to Dockerfile from the repository root | `Dockerfile` |

# Job from go2scale hub --> hub.go2scale.io

stages:

  - build

docker_build:

  stage: build

  image:

    CUSTOM_TAG: ""

    COMMIT_CREATE_LATEST: "false"

    TAG_CREATE_LATEST: "true"

    DOCKERFILE_PATH: "Dockerfile"

  script:

    - mkdir -p /kaniko/.docker/

    - if [ ! -z ${CUSTOM_REGISTRY} ]; then

    - fi

    - if [ ! -z ${CUSTOM_TAG} ]; then

    -   /kaniko/executor --context ${CI_PROJECT_DIR} --dockerfile ${CI_PROJECT_DIR}/Dockerfile --destination ${REGISTRY_IMAGE}:${CUSTOM_TAG}

    -   /kaniko/executor --context ${CI_PROJECT_DIR} --dockerfile ${CI_PROJECT_DIR}/${DOCKERFILE_PATH} --destination ${REGISTRY_IMAGE}:${CUSTOM_TAG}

    - else

    -   /kaniko/executor --context ${CI_PROJECT_DIR} --dockerfile ${CI_PROJECT_DIR}/Dockerfile --destination ${REGISTRY_IMAGE}:${IMAGE_TAG} ${OPTIONAL_TAG}

    -   /kaniko/executor --context ${CI_PROJECT_DIR} --dockerfile ${CI_PROJECT_DIR}/${DOCKERFILE_PATH} --destination ${REGISTRY_IMAGE}:${IMAGE_TAG} ${OPTIONAL_TAG}

    - fi

* Add variable `DOCKERFILE_PATH` which permits specifying custom path to

  Dockerfile