Add nodes by label step

[jetersen]

We have this step in our shared library.
The step enables us to maintain a group of nodes through Jenkins by using their label to get the desired group, ie. 'MacOS' label.
Currently, our shared library step is using the Jenkins JSON API, earlier it was using unsafe groovy methods.
So I suggest we add the step to this plugin 👍

The suggested name for the step is 'nodesByLabel' However I am open for better suggestion, also the package location.

Use case:

@Library('widex') _
def branches = [:]

def nodeNames = nodesByLabel 'macOS'
def XcodeVersion = '9.2'

nodeNames.each { nodeName ->
  branches[nodeName] = {
    node(nodeName) {
      stage("Install Xcode ${XcodeVersion} for ${nodeName}") {
        timeout(time:60, unit:'MINUTES') {
          withCredentials([
            usernamePassword(credentialsId: 'widex.appleid', passwordVariable: 'XCODE_INSTALL_PASSWORD', usernameVariable: 'XCODE_INSTALL_USER')
          ]) {
            sh "xcversion update"
            sh "xcversion install '${XcodeVersion}' --no-progress"
          }
        }
      }
    }
  }
}

parallel branches

[rsandell]

You should not be that type specific here. List<String> is better.

[rsandell]

I18n

If I grok the logic below this statement is not exactly true, since it only lists nodes that are online.
A potential enhancement could be to add an optional parameter allowing the caller to not filter out based on online state?

[jetersen]

Yes, it filters on the online state. So the optional filter would be great 👍

[rsandell]

#36 Is now merged, so you should target master instead.

[jetersen]

@rsandell rebased onto master and added your suggestion.

[rsandell]

I forgot to ask you to update docs/STEPS.md. But there are others missing as well, so if you don't get to it before I start to prepare for release I can add it then.