On Sep 12, 2014, at 05:55 AM, Eric S. Raymond wrote:

>> > 2) "eliz@gnu.org-20101113210758-8ml5kibjtza5ysmb" Um.  What the *hell*?
>> 
>> It's a bzr revision-id.  You can use it in "bzr log" or any other bzr
>> command that accepts a revision spec.
>
>Well, at least that makes it less arbitrary.  But still soon to become
>meaningless, and I still have to fix it.

Almost every $vcs conversion I've ever been a part of (going back to RCS days)
has always kept the old repository around in read-only mode for long enough
time that people no longer care.  I'm currently involved in some svn->git
transitions and we're debating about history and revision reference
preservation[*].  I think the general consensus for us is to keep the old svn
repos around read-only so that *if* such history is required (and it rarely
is, at least IME), the user could go to the svn repo to look something up.
Yes, it's less convenient, but preserving this is also a lot of work for a
rare use case.

I've also heard that git has a way to refer to "external" history, i.e. from
git into svn, so that from git's point of view, you can traverse into logs for
svn history.  But I could be wrong and no nothing more about this than
hearsay.

Maybe Emacs's conversion has different requirements.  I certainly don't mean
to derail the current conversion efforts, just relating previous experience.

Cheers,
-Barry

[*] I may soon be looking at some bzr->git transitions, and I'm wondering if
Eric's code would be generally useful, or is to focused on the vagaries of
Emacs's repo.