List of changes before updating

[Karl Berry]

    If there is currently no way to get changelogs, may I suggest a
    tlmgr update <xxx> --changelog, not doing any actual update, but
    showing a short changelog for the package?

It would be nice, but as far as I can see it's not possible. We can't
create information out of nothing.  All TL and CTAN can do is pass along
what authors provide. And even when change information is available
(rare), there is no way to guess where it might be in order to display it.

I don't think an interface from tlmgr to CTAN announcements is worth the
effort; people can just read the announcements directly. And many
(normal package) updates do not have announcements.

As for TL packaging-only updates, I guess in theory we could extract log
messages out of the repository for the relevant directories and make
them available somehow, but I confess that this sounds like a lot of
work for not much return. The messages are not going to be very
informative.

What I can imagine is an option to diff the package as installed against
the new package on the server, and leave it up to the user to pick out
the interesting pieces. I suspect in most cases the diffs would be so
voluminous that it would be more painful than useful, but it could be
worth a try.

So, one first step would be to write a separate utility that simply
diffs two packages -- that is, tar archives -- and tries to figure out
what's interesting to display. If it turns out to be feasible and
useful, it could be integrated into tlmgr in due time.

Such a thing could also be useful for showing the difference between the
version currently installed and the previous version (if backups aren't
turned off). --best regards, karl.