Prevent Codecov from using "approximate" PR base commits

[nylen]

Per https://docs.codecov.io/v4.3.6/docs/comparing-commits#section-resolution, if Codecov does not find a coverage report for the "base commit" of a pull request (the commit the PR shares in common with master), then it will attempt to find a similar commit and use it as the base.

This causes incorrect coverage results, I suspect it is the reason the report in #2226 is wrong and partly related to the Codecov issues in #2296 as well.

Testing at #2296 seems to indicate that adding this setting has the intended effect, and https://docs.codecov.io/v4.3.6/docs/commit-status seems to indicate that this situation won't cause a build failure due to the default setting of if_not_found: success.

[aduth]

From the code snippet provided in their docs, it seems false is the default value anyways?

check if you allow offsets (default False)

https://docs.codecov.io/v4.3.6/docs/comparing-commits#section-resolution

Would this have any negative impact on rebases since the base commit would change?

[nylen]

Good catch on the default being False, so this shouldn't do anything.

I re-ran my test from #2296 with try/improved-arrow-nav-original-without-codecov-change and try/improved-arrow-nav-original-codecov-try2. This time I saw the same, invalid result on both branches.