This mojo is designed to get a unique build number for each time you build
your project. So while your version may remain constant at 1.0-SNAPSHOT
for many iterations until release, you will have a build number that can
uniquely identify each build during that time. The build number is obtained
from scm, and in particular, at this time, from svn. You can then place that
build number in metadata, which can be accessed from your app, if desired.

The mojo also has a couple of extra functions to ensure you get the proper
build number. First, your local repository is checked to make sure it is
up to date. Second, your local repository is automatically updated, so that
you get the latest build number. Both these functions can be suppressed,
if desired.

Optionally, you can configure this mojo to produce a revision based on a
timestamp, or on a sequence, without requiring any interaction with an
SCM system. Note that currently, the only supported SCM is subversion.