Output clang-format issues in job

Summary

This MR:

• Outputs the clang-format output in the job logs (so that you don't have to always click on the artifacts to see the differences)
• Changes the extension from .out to .diff (as it's outputting a diff file)
• Reduces the amount of stuff git fetch fetches

Additional Required Actions

• Requires manual tests in pre-production: NO
• Requires a documentation update: NO

References

Closes #973 (closed)