This changes tidy to check shell scripts for the proper shebang and
options. It does not check that variables are formatted correctly. It
also adds a check for the MPL 2.0 license in shell scripts.
Added test that files exist to etc/ci/check_no_unwrap.sh.
Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy --faster` does not report any errors
- [X] No github issue.
Either:
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because this PR updates test code.
Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process.
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