job('example') {
parameters {
 activeChoiceParam('CHOICE-1') {
  description('Allows user choose from multiple choices')
  filterable()
  choiceType('SINGLE_SELECT')
  groovyScript {
   // script('["choice1", "choice2"]')
   script('-DYNANIC CHOICES-REF-PESUDO-CODE')
   fallbackScript('"fallback choice"')
  }
 }
}}

groovyScript {
script('
// call git repo and fetch some branches info.
// collect them in some local variable and return them as choices
def branches = "git branch -l"
return branches
')
fallbackScript('"fallback choice"')
}