* build-aux/gitlog-to-changelog-repro.patch: New file.
* Makefile.am (EXTRA_DIST): Add it.
(build-aux/gitlog-to-changelog-repro): New rule.
(gen-ChangeLog): Use 'gitlog-to-changelog-repro'.
(DISTCLEANFILES): Add 'build-aux/gitlog-to-changelog-repro'.