Comment 2 for bug 1695103

There's one downside of this patch: The function "_compute_revno_str()" used to query revision numbers is not overly efficient which results in significantly reduced export performance (approx 3 times slower).

If anybody knows a faster approach let me know.

In any case since this will be a one-time conversion I guess this is acceptable given the fact that revision numbers are quite important as many commit messages reference them.