Why is the spring-boot-maven plugin adding the war itself when repackaging an overlayed war file?

Question

I have the following pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>org.example</groupId>
    <artifactId>foo-war</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>

    <dependencies>
        <dependency>
            <groupId>org.jasig.portlet</groupId>
            <artifactId>CalendarPortlet</artifactId>
            <version>2.6.2</version>
            <type>war</type>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>2.1.6.RELEASE</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>build-info</goal>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.2.3</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                    <overlays>
                        <overlay>
                            <groupId>org.jasig.portlet</groupId>
                            <artifactId>CalendarPortlet</artifactId>
                        </overlay>
                    </overlays>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

When I run mvn package the resulting repackaged war file contains the original war itself under WEB-INF/lib/CalendarPortlet-2.6.2.war.

Why does spring-boot add the war during repackaging and how do I prevent this?

In my real project I want to replace some resources of an already existing war and add the build-info for display by the actuator. But doubling the size of the artifact is not feasible just for that.

EDIT:
The problem also appears when repackaging jars.

Answer 1

Preventing the original artifact being included in the repackaged artifact can be achieved by manually specifying an exlclude for that artifact in the config of the spring-boot-maven plugin:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <version>2.1.6.RELEASE</version>
    <configuration>
        <excludes>
            <exclude>
                <groupId>org.jasig.portlet</groupId>
                <artifactId>CalendarPortlet</artifactId>
            </exclude>
        </excludes>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>build-info</goal>
                <goal>repackage</goal>
            </goals>
        </execution>
    </executions>
</plugin>

But I still don't know why that plugin includes the original artifact in the repackaged one.