How can I perform a one-time bulk copy of system field values to a custom field?

Question

Seems like it should be pretty straightforward, but I haven't found a way.  There seem to be similar questions on here, but not with answers.

If I have a filter with x-number of issues and want to copy a system field of date type to a newly created date field, how can that be done?  For new issues, it will be populated automatically by a post function, but for historic issues I haven't found a method to do this.

Script Runner only works for custom field to custom field.

Bob Swift · Answer

JIRA Command Line Interface (CLI) is often used for doing various bulk operations. In this case, you would use the copyFieldValue action. Front end that with runFromIssueList with a JQL that identifies all the issues you want to update. See How to use runFromIssueList if necessary.

Vasiliy Zverev · Answer

This script copies a value from one custom field to another.

I think you can modify it to your needs. It could be run from script console for scrit Runner. If it suits I can advice how to use it for set of issues

import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.event.type.EventDispatchOption
import com.atlassian.jira.issue.CustomFieldManager
import com.atlassian.jira.issue.Issue
import com.atlassian.jira.issue.IssueManager
import com.atlassian.jira.issue.UpdateIssueRequest
import com.atlassian.jira.issue.fields.CustomField

/**
 * Script for copy value from one custom field to another
 */

IssueManager issueManager = ComponentAccessor.getIssueManager();
Issue issue = issueManager.getIssueByCurrentKey("SN458-1")
if (issue == null)
    return "No such issue"

//Prepare to update
UpdateIssueRequest.UpdateIssueRequestBuilder issueRequestBuilder = new UpdateIssueRequest.UpdateIssueRequestBuilder();
issueRequestBuilder.eventDispatchOption(EventDispatchOption.ISSUE_UPDATED);
issueRequestBuilder.sendMail(false);
UpdateIssueRequest updIssReq = new UpdateIssueRequest(issueRequestBuilder);

CustomFieldManager customFieldManager = ComponentAccessor.getCustomFieldManager();

CustomField cstFld_From = customFieldManager.getCustomFieldObjectByName("Name1");
CustomField cstFld_To = customFieldManager.getCustomFieldObjectByName("Name2");

if(     (cstFld_From == null)
    &&  (cstFld_To == null)
    &&  (cstFld_From.getCustomFieldType() != cstFld_To.getCustomFieldType()
    &&  (cstFld_From != cstFld_To)
    )) {
        issue.setCustomFieldValue(cstFld_To, cstFld_From.getValue(issue))
        issueManager.updateIssue(ComponentAccessor.getJiraAuthenticationContext().getUser(), issue, updIssReq);
}