Thank you @Sembiance and you!
When I somehow get to an old ebuild like perhaps gentoo/www-client/chromium /chromium-118.0.5993.54.ebuild here:
https://github.com/gentoo/gentoo/blob/3fb0eea1ee35033113d7af...
how do I find which gentoo portage 'files' were live at the time? (poor example - there may have been no change in this case.)
Checkout the commit? You'll have a local copy of the tree exactly as it was at that time.
Thank you! I don't live in git and this helps! Normally under gentoo I shouldn't have to. This actual git https://github.com/gentoo/gentoo (as opposed to the gentoo browser view) plus this "checkout the commit" should get me much further. ... And probably deserve some space in the gentoo docs.