[clang-tidy] Headers taken into account

Hi,

I'd like to know how Clang-Tidy actually determines which headers are taken
into account. When I invoke the following command in an out-of-source build,
'run-clang-tidy.py -fix -checks='-*,modernize-*' -header-filter='.*' -p=.'
with 'build/debug' being pwd, all headers contained in '../../src/**' are
taken into account. Does Clang-Tidy look for '.h,.hxx,etc.' pairs matching a
.cpp or does it look for all headers in folders that contain source files?

Cheers,
Alex

run-clang-tidy.py runs clang-tidy over all the files in a compilation database.
clang-tidy checks those files and everything they #include.

Thanks for the explanation.

-Alex