Re: [PATCH v2 10/13] tests: include detailed trace logs with --write-junit-xml upon failure

On Mon, Oct 15, 2018 at 03:12:12AM -0700, Johannes Schindelin via GitGitGadget wrote:

From: Johannes Schindelin <redacted>

The JUnit XML format lends itself to be presented in a powerful UI,
where you can drill down to the information you are interested in very
quickly.

For test failures, this usually means that you want to see the detailed
trace of the failing tests.

With Travis CI, we passed the `--verbose-log` option to get those
traces. However, that seems excessive, as we do not need/use the logs in

As someone who has dug into a few occasional failures found by Travis
CI, I'd say that the output of '--verbose-log -x' is not excessive,
but downright essential.

almost all of those cases: only when a test fails do we have a way to
include the trace.

So let's do something different when using Azure DevOps: let's run all
the tests with `--quiet` first, and only if a failure is encountered,
try to trace the commands as they are executed.

Of course, we cannot turn on `--verbose-log` after the fact. So let's
just re-run the test with all the same options, adding `--verbose-log`.
And then munging the output file into the JUnit XML on the fly.

Note: there is an off chance that re-running the test in verbose mode
"fixes" the failures (and this does happen from time to time!). That is
a possibility we should be able to live with.

Any CI system worth its salt should provide as much information about
any failures as possible, especially when it was lucky enough to
stumble upon a rare and hard to reproduce non-deterministic failure.

Ideally, we would label
this as "Passed upon rerun", and Azure Pipelines even know about that
outcome, but it is not available when using the JUnit XML format for
now:
https://github.com/Microsoft/azure-pipelines-agent/blob/master/src/Agent.Worker/TestResults/JunitResultReader.cs

Signed-off-by: Johannes Schindelin <redacted>