Martin Geisler <mg@lazybytes.net> [Sat, 16 May 2009 11:12:49 +0200] rev 8424
changelog: refuse to add revisions with empty usernames
An empty username or a username with a "\n" will make the revision
text contain two "\n\n" sequences -> corrupt repository.
The problem is that changelog.read expects to find exactly one "\n\n"
separator and thus cannot unpack the revision.