A ChangeLog must be included with every patch submitted.
- Don't add the changelog changes to the patch. Write it as part of the email.
- Separate entries that are meant for different changelog files.
- Add information about related bugs (PRs).
An example of changelog is:
2007-01-27 Manuel Lopez-Ibanez <manu@gcc.gnu.org> PR c++/24924 * c-opts.c (c_common_post_options): Handle C++ post-processing here. Set also -pedantic-errors by default for the preprocessor unless -fpermissive is given. cp/ * decl.c (cxx_init_decl_processing): Move command-line options processing to c-opts.c. testsuite/ * g++.dg/cpp/pedantic-errors.C: New. * g++.dg/cpp/permissive.C: New.
You can find more examples by browsing the archive of gcc-patches mailing list.