Access to package list or manifest in source?

I'm planning on testing out pkgbase for maintaining jail file systems on 
the 14 RELEASE family, including the upcoming 14.1 to 14.2 transition.

I looked for a reasonably clear way to determine the contents of the 
packages without resorting to downloading and examining them.

Perhaps I was looking in the wrong place, but I did not find the 
equivalent of `pkg-plist` in the FreeBSD source repo. I did chase down 
seemingly related commits, such as 2f9966f "packages: add package for 
NTP" which seems to add a `PACKAGE= ntp` notation to around 20 
`Makefile`s, but nothing that I saw that looks like a plist.

Having a plist or manifest would help determining a nearly minimal set 
of base packages that are needed for each jail, especially when it comes 
to libraries or certain utilities that might be needed for traditional 
packages and their rc scripts.

Is this information available without extracting from the 
built/downloaded packages?

If it is only available as a build artifact, it might be valuable to 
provide it along with the packages.

TIA,

Jeff