generating the test matrix for local CI runs

["Laszlo Ersek" <lersek@redhat.com>]

(Sigh, my address book pulled one over me -- resending to the correct
list address now. Please ignore the previous posting that you may have
gotten "in private".)

Hi All,

while I can run specific CI tests locally, using the commands listed at:

https://github.com/tianocore/edk2/tree/master/.pytool
https://github.com/tianocore/edk2/tree/master/ArmVirtPkg/PlatformCI
https://github.com/tianocore/edk2/tree/master/OvmfPkg/PlatformCI

I don't know how I can determine and drive the whole "test plan" locally.

When I submit a PR to github, "something" generates (say) 83 test cases.
How can I run that "something" locally?

Assume I have the following:
- a Linux builder VM, with up-to-date tools,
- a Windows builder VM, with up-to-date tools,
- a topic branch, on top of "master".

How do I generate and run those same 83 tests, locally?

It has happened to me that all my local CI steps succeeded (meaning both
the Windows and the Linux builder), but github still rejected the PR --
the reason was that I failed to think of a particular test that github
would run. Composing 83 "stuart" command lines isn't something I'd like
to do manually.

Thanks
Laszlo