Java 7 compatibility silently broken

[RyanFoulds]

The latest versions-maven-plugin (2.9.0) is compiled on java 8. The command used to invoke that plugin will, without special care, use the latest version. ​Could this dependency be explicitly declared or a known-good version be pinned? Perhaps even a configuration parameter to specify the version of versions-maven-plugin to be used?

This issue can easily be worked-around by using specifying a version in a pluginManagement element of a java 7 project using this plugin, but diagnosing the release pipeline failure was tricky without the dependency on versions being declared.

<build>
    <pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>versions-maven-plugin</artifactId>
                <version>2.8.1</version>
            </plugin>
       </plugins>
    </pluginManagement>
</build>

edit: this also applies to the tycho versions plugin which broke support for Java 7 back in version 0.25.0 and now requires at least Java 11.

[aleksandr-m]

Related #115

[aleksandr-m]

Added versionsMavenPluginVersion and tychoVersionsPluginVersion properties with defaults.