[MPLUGIN-384] restore compatibility with Maven 3 ecosystem

.gitignore

@@ -14,3 +14,4 @@ out/
 .DS_Store
 
 .java-version
+.factorypath

maven-plugin-plugin/src/main/java/org/apache/maven/plugin/plugin/metadata/GroupRepositoryMetadata.java → maven-plugin-plugin/src/main/java/org/apache/maven/artifact/repository/metadata/GroupRepositoryMetadata.java

@@ -1,4 +1,4 @@
-package org.apache.maven.plugin.plugin.metadata;
+package org.apache.maven.artifact.repository.metadata;
 
 /*
  * Licensed to the Apache Software Foundation (ASF) under one
@@ -23,12 +23,11 @@
 import java.util.List;
 
 import org.apache.maven.artifact.repository.ArtifactRepository;
-import org.apache.maven.artifact.repository.metadata.AbstractRepositoryMetadata;
-import org.apache.maven.artifact.repository.metadata.Metadata;
-import org.apache.maven.artifact.repository.metadata.Plugin;
 
 /**
  * Metadata for the group directory of the repository.
+ * Class copied from maven-compat for to remove dependency but keep compatibility with Maven 3 (and Nexus Staging
+ * Plugin, see <a href="https://issues.apache.org/jira/browse/MPLUGIN-384">MPLUGIN-384</a>)
  *
  * @author <a href="mailto:[email protected]">Brett Porter</a>
  */

maven-plugin-plugin/src/main/java/org/apache/maven/plugin/plugin/metadata/AddPluginArtifactMetadataMojo.java

@@ -21,6 +21,7 @@
 
 import org.apache.maven.artifact.Artifact;
 import org.apache.maven.artifact.repository.metadata.ArtifactRepositoryMetadata;
+import org.apache.maven.artifact.repository.metadata.GroupRepositoryMetadata;
 import org.apache.maven.artifact.repository.metadata.Versioning;
 import org.apache.maven.plugin.AbstractMojo;
 import org.apache.maven.plugin.MojoExecutionException;