Summary:
Placing `STOPSHIP` or `stopship` (or any case variant) in any file
tracked by Git will now cause a `yarn travis` failure. If you need to
use this string, you can concatenate it as `"stop" + "ship"` or
equivalent.
Test Plan:
In `travis.js`, change `"check-stop" + "ships"` to `"check-stopships"`,
and note that this causes the build to fail with a nice message. Note
that this also causes `check-stopships.sh` to fail even when invoked
from an unrelated directory, like `src`.
wchargin-branch: check-stopships
William Chargin