Bind :clean to 'clean' phase by default

Author: pzygielo

src/it/projects/profile-with-deps-inherit-parent-depMgmt-flatten-dep-all-oss-bom/pom.xml

@@ -30,7 +30,6 @@
           <!-- ensure proper cleanup -->
           <execution>
             <id>flatten.clean</id>
-            <phase>clean</phase>
             <goals>
               <goal>clean</goal>
             </goals>

src/it/projects/system-scope-dep-variable/pom.xml

@@ -44,7 +44,6 @@
           </execution>
           <execution>
             <id>flatten.clean</id>
-            <phase>clean</phase>
             <goals>
               <goal>clean</goal>
             </goals>

src/main/java/org/codehaus/mojo/flatten/CleanMojo.java

@@ -23,6 +23,7 @@
 
 import org.apache.maven.plugin.MojoExecutionException;
 import org.apache.maven.plugin.MojoFailureException;
+import org.apache.maven.plugins.annotations.LifecyclePhase;
 import org.apache.maven.plugins.annotations.Mojo;
 import org.apache.maven.plugins.annotations.Parameter;
 
@@ -37,6 +38,7 @@
  */
 @Mojo(
         name = "clean",
+        defaultPhase = LifecyclePhase.CLEAN,
         requiresProject = true,
         requiresDirectInvocation = false,
         executionStrategy = "once-per-session",

src/site/xdoc/usage.xml.vm

@@ -30,7 +30,6 @@
           <!-- ensure proper cleanup -->
           <execution>
             <id>flatten.clean</id>
-            <phase>clean</phase>
             <goals>
               <goal>clean</goal>
             </goals>