Mercurial - like some other distributed version control systems works such that each developer has a full value repository - there is no real master other than by convention in a team.
To set up your maven project so that the scm configuration points to a developers local repo:
<scm>
<connection>scm:hg:file://${basedir}</connection>
<developerConnection>scm:hg:file://${basedir}</developerConnection>
</scm>
