coverage: introduce ONLY_EXTRA_QUERY_PATHS

[junr03]

Description: introduce an environment variable that allows consuming projects to only run coverage over private extensions.
Risk Level: low
Testing: locally with Envoy Mobile as a consuming project. And existing coverage run in CI
Docs Changes: inline comment

Signed-off-by: Jose Nino jnino@lyft.com

[junr03]

updated @lizan

[asraa]

This PR caused some regression when running coverage locally

test/run_envoy_bazel_coverage.sh

I believe this line shouldn't be run when $COVERAGE_TARGETS is just //test/... I hit some error here. I don't know why it doesn't get hit in CI when CI also runs with //test/...

envoy/test/coverage/gen_build.sh

Line 37 in c2a6373

TARGETS="$TARGETS $("${BAZEL_BIN}" query ${BAZEL_QUERY_OPTIONS} "attr('tags', 'coverage_test_lib', ${REPOSITORY}${target})" | grep "^//")"

Is that right? @junr03

Edit: disregard, sorry about that! whatever problem is happening with me running local coverage is from sometime after this, but the failure just pointed to something around there. works before the bazel 3.0 bump

[junr03]

@asraa ok, do let me know if you find any problems!