src/it/projects/basic-features/massembly-351-projectPrefixInterp/src/main/assembly/myassembly.xml

<?xml version="1.0" encoding="UTF-8"?>

<assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0 http://maven.apache.org/xsd/assembly-1.1.0.xsd">
    <id>myassembly</id>
    <formats>
        <format>dir</format>
    </formats>
    <includeBaseDirectory>false</includeBaseDirectory>
    <fileSets>
        <fileSet>
            <directory>src/main/files</directory>
            <outputDirectory>/files</outputDirectory>
            <includes>
              <include>${artifactId}1.file</include>
            </includes>
        </fileSet>
        <fileSet>
            <directory>src/main/files</directory>
            <outputDirectory>/files</outputDirectory>
            <includes>
              <include>${pom.artifactId}2.file</include>
            </includes>
        </fileSet>
        <fileSet>
            <directory>src/main/files</directory>
            <outputDirectory>/files</outputDirectory>
            <includes>
              <include>${project.artifactId}3.file</include>
            </includes>
        </fileSet>
    </fileSets>
</assembly>