build.xml

<project name="Builder" default="init" basedir=".">
    <description>
        ...
    </description>
    <!-- set global properties for this build -->
    <property name="src" location="./core/src"/>

    <tstamp>
        <format property="TODAY_MY" pattern="yyyyMMdd-HHmm"  locale="en,US" />
    </tstamp>

    <target name="init">
        <buildnumber/>
        <replaceregexp file="${src}/main/java/me/vrekt/oasis/OasisGame.java"
                       match="public\s+static\s+final\s+String\s+GAME_VERSION\s+=\s+&quot;.*&quot;;"
                       replace="public static final String GAME_VERSION = &quot;${TODAY_MY}-${build.number}&quot;;"
                       byline="true"
        />
    </target>
</project>