Changelog should only take commit message until the first empty line

[Michał Sawicz]

It's a convention to do:

"""
Brief description of commit

Verbose description of what the commit does and why, often
spanning
many
lines.
"""

When this ends up in changelogs as a whole, is quite unreadable and isn't really look log-like. It'd be nice if the train would only take the commit message until an empty newline, leaving the verbose part in the commit message alone.