Patch to git_changelog for release note creation

I would like to apply the attached patch to git_changelog for use in
creating the major release notes.  I specifically added these flags:

    --author-after  Show author after the commit
    --master-only   Show commits made exclusively to the master branch
    --reverse-order Show commits in reverse date order

The default output is unaffected.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +