This Plugin gives some very
nice benefits, like running scripts in Transitions.
Sample - This actually gets hold on a clone and changes the "Task Type" Custom Field to "Clone", whereas on the Master it is still "Master"
import com.atlassian.jira.ComponentManager
import com.atlassian.jira.issue.customfields.manager.OptionsManager
def componentManager = ComponentManager.instance
def optionsManager = componentManager.getComponentInstanceOfType(OptionsManager.class)
def cf = customFieldManager.getCustomFieldObjects(issue).find {it.name == 'Task Type'}
def fieldConfig = cf.getRelevantConfig(issue)
def optionClone = optionsManager.getOptions(fieldConfig).find {it.value == "Clone"}
issue.setCustomFieldValue(cf, optionClone)