chore: Expand README with more details and examples for working CI with buildx...

chore: Expand README with more details and examples for working CI with buildx and semantic release.

README.md

+##### Fork of https://github.com/jdrouet/docker-with-buildx -> git.griefed.de -> github.com/Griefed
+
+# Docker image with buildx pre-installed
+
+# Setup 
+
+:warning: **Requires CI/CD variable `GITLAB_TOKEN` with personal-access-token (read/write permision to registry and repository).**
+
+:warning: **Requires CI/CD variable `DOCKERHUB_USER` with lowercase username of the Dockerhub repository owner where the image will be pushed to.**
+
+:warning: **Requires CI/CD variable `DOCKERHUB_REPO` with lowercase name of the Dockerhub repository where the image will be pushed to.**
+
+:warning: **Requires CI/CD variable `DOCKERHUB_TOKEN` with personal-access-token to Docherhub.**
+
+Currently it's doing:
+- bump up semantic version (major/minor/patch) according commit [prefixes](https://github.com/angular/angular.js/blob/master/DEVELOPERS.md#type)
+- create tag with release version
+- create release for new tag
+- update [CHANGELOG.md](CHANGELOG.md) with release notes generated from commits
+- commit & push all above steps
+
+# Example setup files
+
+## GitLab Runner config.toml
+Example config.toml for a GitLab-Runner which works with a dockerized GitLab and multiarch Docker images using buildx:
+
+```toml
+concurrent = 1
+check_interval = 0
+
+[session_server]
+  session_timeout = 1800
+
+[[runners]]
+  name = "Runner-One"
+  url = "https://url.to.your.gitlab"
+  token = "token_generated_by_runner_registration"
+  executor = "docker"
+  environment = ["DOCKER_TLS_CERTDIR="]
+  [runners.custom_build_dir]
+  [runners.cache]
+    [runners.cache.s3]
+    [runners.cache.gcs]
+    [runners.cache.azure]
+  [runners.docker]
+    tls_verify = false
+    image = "ubuntu:20.04"
+    privileged = true
+    disable_entrypoint_overwrite = false
+    oom_kill_disable = false
+    disable_cache = false
+    cache_dir = "/cache"
+    volumes = ["/var/run/docker.sock:/var/run/docker.sock", "/cache"]
+    shm_size = 0
+```
+
+## GitLab .gitlab-ci.yml
+Example of a GitLab CI comosed of three stages: test, release and build
+
+```yml
+stages:
+  - test
+  - release
+  - build
+
+test docker:
+  stage: test
+  image: griefed/docker-with-buildx:latest
+  services:
+    - name: docker:dind
+      alias: docker
+  variables:
+    project_name: $CI_PROJECT_NAME
+    SEMANTIC_RELEASE_PACKAGE: $CI_PROJECT_NAME
+  before_script:
+    - docker login -u "$DOCKERHUB_USER" -p "$DOCKERHUB_TOKEN" docker.io
+    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
+    - docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
+    - docker buildx create --use --name mybuilder
+  script:
+    - docker pull "$CI_REGISTRY_IMAGE:develop"
+    - docker buildx build
+      --push
+      --platform linux/amd64,linux/arm/v7,linux/arm64
+      --cache-from "$CI_REGISTRY_IMAGE:develop"
+      --tag "$CI_REGISTRY_IMAGE:develop"
+      --tag "index.docker.io/$DOCKERHUB_USER/$DOCKERHUB_REPO:develop" .
+  except:
+    refs:
+      - tags
+    variables:
+      - $CI_COMMIT_TITLE =~ /^RELEASE:.+$/
+
+release:
+  needs: ['test docker']
+  stage: release
+  image: griefed/gitlab-semantic-release:latest
+  services:
+    - name: docker:dind
+      alias: docker
+  variables:
+    project_name: $CI_PROJECT_NAME
+    SEMANTIC_RELEASE_PACKAGE: $CI_PROJECT_NAME
+  script:
+    - npx semantic-release
+  only:
+    - master
+  except:
+    refs:
+      - tags
+    variables:
+      - $CI_COMMIT_TITLE =~ /^RELEASE:.+$/
+
+build:
+  stage: build
+  image: griefed/docker-with-buildx:latest
+  services:
+    - name: docker:dind
+      alias: docker
+  variables:
+    project_name: $CI_PROJECT_NAME
+    SEMANTIC_RELEASE_PACKAGE: $CI_PROJECT_NAME
+  before_script:
+    - docker login -u "$DOCKERHUB_USER" -p "$DOCKERHUB_TOKEN" docker.io
+    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
+    - docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
+    - docker buildx create --use --name mybuilder
+  script:
+    - docker pull "$CI_REGISTRY_IMAGE:latest"
+    - docker buildx build
+      --push
+      --platform linux/amd64,linux/arm/v7,linux/arm64
+      --cache-from "$CI_REGISTRY_IMAGE:latest"
+      --tag "$CI_REGISTRY_IMAGE:latest"
+      --tag "index.docker.io/$DOCKERHUB_USER/$DOCKERHUB_REPO:$CI_COMMIT_TAG"
+      --tag "index.docker.io/$DOCKERHUB_USER/$DOCKERHUB_REPO:latest" .
+  only:
+    - tags
+```
+
+## Semantic-Release .releaserc.yml
+Example config for changelog, tag and release generating config file using conventional commits.
+
+```yml
+branches: ['master','main']
+ci: true
+debug: true
+dryRun: false
+tagFormat: '${version}'
+
+# Global plugin options (will be passed to all plugins)
+preset: 'conventionalcommits'
+gitlabUrl: 'https://url.to.your.gitlab' # your gitlab url
+
+# Responsible for verifying conditions necessary to proceed with the release:
+# configuration is correct, authentication token are valid, etc...
+verifyConditions:
+  - '@semantic-release/changelog'
+  - '@semantic-release/git'
+  - '@semantic-release/gitlab'
+
+# Responsible for determining the type of the next release (major, minor or patch).
+# If multiple plugins with a analyzeCommits step are defined, the release type will be
+# the highest one among plugins output.
+# Look details at: https://github.com/semantic-release/commit-analyzer#configuration
+analyzeCommits:
+  - path: '@semantic-release/commit-analyzer'
+    releaseRules:
+      - breaking: true
+        release: major
+      - type: build     # Changes that affect the build system or external dependencies
+        release: patch
+      - type: chore     # Other changes that don't modify src or test files
+        release: false
+      - type: ci        # Changes to our CI configuration files and scripts
+        release: false
+      - type: docs      # Documentation only changes
+        release: false
+      - type: feat      # A new feature
+        release: minor
+      - type: fix       # A bug fix
+        release: patch
+      - type: perf      # A code change that improves performance
+        release: patch
+      - type: refactor  # A code change that neither fixes a bug nor adds a feature
+        release: false
+      - type: revert    # Reverts a previous commit
+        release: patch
+      - type: style     # Changes that do not affect the meaning of the code
+        release: false
+      - type: test      # Adding missing tests or correcting existing tests
+        release: false
+
+# Responsible for generating the content of the release note.
+# If multiple plugins with a generateNotes step are defined,
+# the release notes will be the result of the concatenation of each plugin output.
+generateNotes:
+  - path: '@semantic-release/release-notes-generator'
+    writerOpts:
+      groupBy: 'type'
+      commitGroupsSort: 'title'
+      commitsSort: 'header'
+    linkCompare: true
+    linkReferences: true
+    presetConfig:
+      types:  # looks like it only works with 'conventionalcommits' preset
+        - type: 'build'
+          section: '🦊 CI/CD'
+          hidden: false
+        - type: 'chore'
+          section: 'Other'
+          hidden: false
+        - type: 'ci'
+          section: '🦊 CI/CD'
+          hidden: false
+        - type: 'docs'
+          section: '📔 Docs'
+          hidden: false
+        - type: 'example'
+          section: '📝 Examples'
+          hidden: false
+        - type: 'feat'
+          section: '🚀 Features'
+          hidden: false
+        - type: 'fix'
+          section: '🛠 Fixes'
+          hidden: false
+        - type: 'perf'
+          section: '⏩ Performance'
+        - type: 'refactor'
+          section: ':scissors: Refactor'
+          hidden: false
+        - type: 'revert'
+          section: '👀 Reverts'
+        - type: 'style'
+          section: '💈 Style'
+        - type: 'test'
+          section: '🧪 Tests'
+          hidden: false
+
+# Responsible for preparing the release, for example creating or updating files
+# such as package.json, CHANGELOG.md, documentation or compiled assets
+# and pushing a commit.
+prepare:
+  # - path: '@semantic-release/exec'
+  #   # Execute shell command to set package version
+  #   cmd: './deployment/version-plaintext-set.sh ${nextRelease.version}'
+  # - path: '@semantic-release/exec'
+  #   cmd: './deployment/version-oas-set.sh ${nextRelease.version} openapi.yaml'
+  # - path: '@semantic-release/exec'
+  #   verifyReleaseCmd: "echo ${nextRelease.version} > VERSION.txt"
+  - path: '@semantic-release/changelog'
+    # Create or update the changelog file in the local project repository
+  - path: '@semantic-release/git'
+    # Push a release commit and tag, including configurable files
+    message: 'RELEASE: ${nextRelease.version}'
+    assets: ['CHANGELOG.md']
+
+# Responsible for publishing the release.
+publish:
+  - path: '@semantic-release/gitlab'
+    # Publish a GitLab release
+    #  (https://docs.gitlab.com/ce/user/project/releases/index.html#add-release-notes-to-git-tags)
+
+success: false
+
+fail: false
+```

readme.md

-# docker image with buildx installed
-
-To build the image, you just have to run
-
-```bash
-docker build -t docker-with-buildx .
-```