change_customer_field_to_labels.rb

proj_id = 10010

search_svc = jira.component_mgr.getSearchService

q = search_svc.parseQuery(jira.user('eanderson'), "project=qa and Customer is not empty").getQuery
res = search_svc.search(jira.user('eanderson'), q, com.atlassian.jira.web.bean.PagerFilter.getUnlimitedFilter())

res.getIssues.each do |issue|
  cf = jira.custom_field(issue, "Customer")
  issue.getCustomFieldValue(cf).split(",").map{|x| x.strip.gsub(' ', '_')}.each do |label|
    jira.label_mgr.addLabel(jira.user('eanderson'), issue.getId, 10480, label, false)
  end
end

quick_jira_test.rb

issue = jira.get_issue('QA-45047') # FIXME: hack for development

cf = jira.custom_field(issue, "Customer")
labels = issue.getCustomFieldValue(cf).split(",").map{|x| x.strip.gusb(' ', '_')}

labels.each do |label|
  jira.label_mgr.addLabel(jira.user('eanderson'), issue.getId, 10480, label, false)
end