I see several possibilities here:
- Whenever an upgrade results in a changed default copy (that way admins can check whether those changes are what they want or whether they need to customize)
- Whenever an upgrade results in a changed default copy AND the site is currently not using the default copy (here the aim would merely be to alert admins to the existence of a new copy which they would never see because they are using a customized version)
- Whenever an upgrade results in a default copy that is different to the default copy that was in place when the customized copy was first created AND the site is currently not using the default copy (this would ensure that the change notifications remain visible even across multiple upgrades, even when the latest upgrade did not result in any changes)
My preference is between 1 and 3. #1 because of it’s simplicity (as far as I can tell), and #3 because of its rigidity.
I didn’t include a mockup in the OP because I didn’t see it so much as a UI issue but simply a matter of being somehow informed, whatever is the simplest way to achieve this. But if you ask me for a visualization, here is one (which obviously combines several scenarios in one image):
In addition (or perhaps as the only way), there could also another filter check-box:
To alert admins that there are updated copies, there could also be a notice at the very end of the upgrade CLI screen.
I just realized that the buttons should probably say “show recent changes” and “show default”. But nevermind.