How to pick up the changes immediately after editing the .vm files in email templates?

[Steve]

We are running on a Jira Data Center instance of version 8.20.12 and would like to customize our email templates. The way we have been doing this is

1. Download .zip from System -> Mail -> Email templates

2. Make changes to .vm files

3. Save the changes and upload .zip

And we were able to see the changes. However, such a downloading-uploading loop is cumbersome and not ideal for version control. I've read this article  https://confluence.atlassian.com/adminjiraserver0820/customizing-email-content-in-jira-server-1095777454.html

and performed the following in the "Optional: Deploying Velocity templates without restarting Jira" section:

From <jira-install>/atlassian-jira/WEB-INF/classes/velocity.properties:

1. Change class.resource.loader.cache from true to false
2. Remove the comment sign (#) from #velocimacro.library.autoreload=true

We could not see the changes being picked up by Jira without an upload. For a data center instance, we'd like to know if there's a way that we can let Jira pick up changes immediately.

[Steve]

1. Is there a way to disable/clear the cache?

2. Is there a command that we can use to force that?

3. Is there a way to restart velocity template without restarting the Jira instance