Advanced apitrace usage for GL driver development

[José Fonseca]

FYI, I documented examples of more advanced debugging techniques using
apitrace, meant specifically for GL driver development (as opposed to
GL application development). In particular:

- how to prepare a regression test case (*)

- how to automate git bisect to find a commit which introduced a regression

- how to replay a trace side-by-side with a reference GL
implementation (e,g, an old stable build, or a software renderer), and
pinpoint which draw call a mismatch first occurs

These are all techniques that I've successfully used several times now
-- true time savers --, and hoped to blog about, but never got around
to write up properly.

So, if you ever have an use case for these techniques, please read
https://github.com/apitrace/apitrace/blob/master/README.markdown for
more details. And feel free to contact me if the instructions are
incomplete or don't work for you.

Jose

(*) a test suite would also be certainly feasible, but it is still a
bit crude for now, as scripts to aggregate and present results for
many test cases are still missing from apitrace