The script generate-future-functions.py writes C code to support the mock server test framework. This code predates our clang-format style and doesn't conform. On occasion we accidentally apply clang-format to the generated code, which makes a big diff, and the next time we generate it the style changes back, which makes another big diff.
Update the code generator to conform to clang-format, or add a step to the code generator to call clang-format on its output, or find a way to prevent its output from ever being accidentally formatted.