Add a .gitattributes file for use with git-merge-changelog

Add a .gitattributes file for use with git-merge-changelog

Individual users will still have to:

 1. Install git-merge-changelog

 2. Set up the merge driver in their git config

See gnulib's lib/git-merge-changelog.c [1] for details.

For example, I:

 1. Patched Debian's gnulib package to build git-merge-changelog, and
    sent the patch to the Debian maintainer, who then proceeded to not
    only accept my patch but even write a *manpage* for
    git-merge-changelog! (Let's hear it for Ian Beckwith.)

    So now, I can install it simply by running "apt-get install
    git-merge-changelog".  (Except, of course, that I already have it
    installed from when I was testing my patch.)

 2. Did step (2) from .gitattributes

With this patch applied and the above two steps done by whatever means
you deem best, you can say goodbye to merge conflicts in ChangeLog
files -- at least *IF* people stop renaming the danged things, anyway.

If you don't do step 2, you will continue to suffer from ChangeLog
merge conflicts exactly as before, whether or not you did step 1.

If you do step 2 but not step 1, git will likely start complaining
that it can't find any "git-merge-changelog" to run.

[1]: http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=lib/git-merge-changelog.c

[Note: The docs for git-merge-changelog (the comments at the top) say
that you need a .gitattributes in every directory.  The docs are wrong.
Ignore the docs.  Well, not the whole docs; just that part.

You really only need one at the top level, since .gitattributes uses
the same pattern matching rules as .gitignore, which match files in
any subdirectory unless you prefix the pattern with a "/", as
explained in the gitignore(5) manpage.]