String SELF_COMBINATION_MODE_ATTRIBUTE = "combine.self";

    String SELF_COMBINATION_OVERRIDE = "override";

    String SELF_COMBINATION_MERGE = "merge";

    String SELF_COMBINATION_REMOVE = "remove";

    /**
     * In case of complex XML structures, combining can be done based on id.
     */
    String ID_COMBINATION_MODE_ATTRIBUTE = "combine.id";

    /**

    RepositorySystemSession getRepositorySession();

    ProjectBuildingRequest setRepositorySession(RepositorySystemSession repositorySession);

    /**
     * Sets the merge mode used to combine repositories declared in the POM with the repositories specified in this
     * request.
     *
     * @param mode The repository merge mode, must not be {@code null}.

  <version>1.0</version>
  <packaging>pom</packaging>

  <name>Maven Integration Test :: MNG-2591</name>
  <description>
    Test aggregation of list configuration items for build plugins when using
    'combine.children=append' attribute.
  </description>

  <modules>
    <module>subproject</module>
  </modules>

  <build>
    <pluginManagement>
      <plugins>
        <plugin>

        this.scopes = new HashSet<>();

        addScopes(scopes);
    }

    /**
     * Creates a new filter that combines the specified filters.
     *
     * @param filters The filters to combine, may be {@code null}.
     */
    public CumulativeScopeArtifactFilter(CumulativeScopeArtifactFilter... filters) {
        this.scopes = new HashSet<>();

          <stringParams combine.children="append">
            <!-- NOTE: These values are deliberately not in alpha order! -->
            <stringParam>CHILD-1</stringParam>
            <stringParam>CHILD-3</stringParam>
            <stringParam>CHILD-2</stringParam>
            <stringParam>CHILD-4</stringParam>
          </stringParams>
          <listParam combine.children="append">

  <version>1.0</version>
  <packaging>pom</packaging>

  <name>Maven Integration Test :: MNG-2591</name>
  <description>
    Test aggregation of list configuration items for build plugins when using
    'combine.children=append' attribute.
  </description>

  <modules>
    <module>subproject</module>
  </modules>

  <build>
    <pluginManagement>
      <plugins>
        <plugin>

          <stringParams combine.children="append">
            <!-- NOTE: These values are deliberately not in alpha order! -->
            <stringParam>CHILD-1</stringParam>
            <stringParam>CHILD-3</stringParam>
            <stringParam>CHILD-2</stringParam>
            <stringParam>CHILD-4</stringParam>
          </stringParams>
          <listParam combine.children="append">

      <plugin>
        <groupId>org.apache.maven.its.plugins</groupId>
        <artifactId>maven-it-plugin-configuration</artifactId>
        <version>2.1-SNAPSHOT</version>
        <configuration>
          <stringParams combine.children="append">
            <stringParam>  childParam  </stringParam>
            <stringParam xml:space="preserve">  preserve space  </stringParam>
          </stringParams>
        </configuration>
      </plugin>

    </dependency>

    <dependency>
      <groupId>maven-test-compile</groupId>
      <artifactId>scope-runtime</artifactId>
      <version>1.0</version>
      <scope>runtime</scope>
    </dependency>

    <dependency>
      <groupId>maven-test-compile</groupId>
      <artifactId>scope-compile</artifactId>
      <version>1.0</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

    public static final String DS_COMPILE = "compile";
    public static final String DS_RUNTIME = "runtime";
    public static final String DS_PROVIDED = "provided";
    public static final String DS_SYSTEM = "system";
    public static final String DS_TEST = "test";
    public static final String RS_NONE = "none";
    public static final String RS_MAIN_COMPILE = "main-compile";