* @return The project's class realm or {@code null}.
     */
    public ClassRealm getClassRealm() {
        return classRealm;
    }

    /**
     * Sets the artifact filter used to exclude shared extension artifacts from plugin realms. <strong>Warning:</strong>
     * This is an internal utility method that is only public for technical reasons, it is not part of the public API.

    server processes which work by conversing over a port may fail.

  * Not all "remote" repositories will fail. Specifically, if the remote
    repo uses the file:// protocol, and it doesn't refer to a shared
    filesystem, it will continue to be available.

  The question remaining is: Which level of offline mode will we support? It
  seems reasonable to assume that users will be able to tell when localhost is

         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <!-- Shared parent. Doesn't define a lot of things about Apache like general mailing lists, but does
       define the settings common to all projects at Apache -->
  <groupId>org.apache</groupId>
  <artifactId>apache</artifactId>

import org.apache.maven.artifact.repository.ArtifactRepositoryPolicy;
import org.apache.maven.metadata.v4.MetadataStaxReader;
import org.apache.maven.metadata.v4.MetadataStaxWriter;

/**
 * Shared methods of the repository metadata handling.
 *
 */
@Deprecated
public abstract class AbstractRepositoryMetadata implements RepositoryMetadata {
    private static final String LS = System.lineSeparator();

     * @param artifactId never {@code null}
     * @param version can be {@code null}
     * @return the matching model or {@code null}
     * @throws IllegalStateException if version was null and multiple modules share the same groupId + artifactId
     */
    public Model get(String groupId, String artifactId, String version) {
        return modelsByGa.getOrDefault(new GAKey(groupId, artifactId), Collections.emptySet()).stream()

     */
    @Nonnull
    @Override
    public String option(Iterable<? extends Path> paths) {
        return format(null, paths);
    }

    /**
     * Implementation shared with {@link Modular}.
     */
    String format(String moduleName, Iterable<? extends Path> paths) {
        if (option == null) {
            throw new IllegalStateException("No option is associated to this path type.");

 * is thread safe.
 * <p>
 * Important: Given the instance of supplier memorizes the supplier {@link RepositorySystem} instance it supplies,
 * their lifecycle is shared as well: once supplied repository system is shut-down, this instance becomes closed as
 * well. Any subsequent {@code getXXX} method invocation attempt will fail with {@link IllegalStateException}.
 */

              <exclude>src/assembly/shared/init</exclude>
              <exclude>src/assembly/shared/init.cmd</exclude>
              <exclude>src/assembly/shared/mvnlauncher</exclude>
              <exclude>src/assembly/shared/mvnlauncher.cmd</exclude>
              <exclude>src/assembly/shared/mvnvalidate</exclude>
              <exclude>src/assembly/shared/mvnvalidate.cmd</exclude>

            if (relocatedArtifact != null) {
                if (withinSameGav(relocatedArtifact, a)) {
                    result.setArtifact(relocatedArtifact);
                    return model; // they share same model
                } else {
                    result.addRelocation(a);
                    a = relocatedArtifact;
                    result.setArtifact(a);
                }
            } else {

            } else {
                repoMetadata.setMetadata(metadata);
                setRepository = true;
            }
        }
        return setRepository;
    }

    /*
     * TODO share with DefaultPluginMappingManager.
     */
    protected Metadata readMetadata(File mappingFile) throws RepositoryMetadataReadException {

        try (InputStream in = Files.newInputStream(mappingFile.toPath())) {