Dear Maintainer,
There is/was no upstream changelog with xdelta3. The only changelog is
the debian changelog which doesn't tell/share what changes were made
in a new release.

For e.g. from the recent changelog.

xdelta3 (3.0.8-dfsg-1) unstable; urgency=low

  * new upstream release (only minor changes)
  * Bug fix: "Please add watch file", thanks to Dmitry Shachnev (Closes:
    #735273).

Hi,

This seems like an issue with upstream not providing a changelog. I
think it would be quite time-consuming for the maintainer to maintain an
upstream changelog themself. Anyway, since this package is not moving
that much sinche 2017 or so, maybe we can close this bug (or mark as
wontfix?).

Bests,

Romain.

At bottom :-

That is upto you, although don't think it should be that hard when you
have git log. Just having git log in a nice way would probably be more
than enough of a changelog but that is upto you. I believe it is
something like git log --pretty or some switch like that which perhaps
just needs to be outputted into changelog and gzipped.

If and when it does get updated, just get the new one on top of it
with the version number.

But again, I leave it in your expert ends as to what you think is
best. If you feel won't fix is the answer, go ahead no issues :(