release automation tool

gistfile1.txt

```
tagname = "https://api.github.com/repos/jenkins-infra/plugin-site-api/releases/latest".tag_name,

if not tagname in "https://hub.docker.com/v2/repositories/jenkinsciinfra/plugin-site/tags?page_size=1000" {
  docker build -t jenkinsinfra/pluginsite:$tagname
  docker push 
}

if tagname != "https://github.com/jenkins-infra/charts/blob/master/charts/plugin-site/values.yaml".image.repository
  update yaml file "https://github.com/jenkins-infra/charts/blob/master/charts/plugin-site/values.yaml"
  git add https//github.com/jenkins-infra/charts/blob/master/charts/plugin-site/values.yaml
  git commit https//github.com/jenkins-infra/charts/blob/master/charts/plugin-site/values.yaml
  git push
```

# parameters:
* github.org:
* github.repository
* dockerhub.organisation
* dockerhub.repository
* version (default to latest)

# credentials:
git push permission
dockerhub credential

# const
DOCKERHUB_URL: https://hub.docker.com/v2/repositories/${dockerhub.organisation}/${dockerhub.repository}/tags?page_size=1000
GITHUB_URL: https://api.github.com/repos/${github.org}/${github.repository}/releases/latest