We could setup a builder that discovers the set of all packages included for all boards, then for each package, maps to the source repo, processes COMMIT_QUEUE.ini for that repo, and verifies (and/or generates) the list of PreCQ builders needed for Unittest / VMTest coverage.

I'm not actually certain what's needed to build that set of pacakges and the associated git repos, so I'm not certain how hard this would be to do.

setup_board would be sufficient to start probing dependency graphs

Running setup_board for all boards in a single chroot is something we already do for binhost test.

What's the best way to map an ebuild to a git repository in the manifest? Are there tools, or do we just parse the ebuild directly?

if you're looking at cros-workon packages, there are helpers in portage_util.py for getting source repo details out of it.  for other ebuilds, you can look at their source repo* to map to an ebuild overlay, but that's as far as you can get easily.  which should be good enough i think.

*: Look at the BuildPackages output to see what i mean:
[ebuild     U  ] chromeos-base/libweave-0.0.1-r659::chromiumos [0.0.1-r658::chromiumos] to /build/amd64-generic/ USE="cros-debug -asan -cros_host -profiling {-test*}" 0 KiB

the "::chromiumos" part says it's coming from the chromiumos-overlay.

Thanks. That's looking feasible, if not trivial.

Hi, this bug has not been updated recently and remains untriaged. Please acknowledge the bug and provide status within two weeks (6/8/2018), or the bug will be closed. Thank you.

CI should triage this, and evaluate if it's still relevant.