#453 update Reproducible Builds outputTimestamp when setting version

.gitignore

@@ -4,3 +4,4 @@ target
 .project
 *.iml
 .idea
+/.factorypath

src/it/it-set-019-outputTimestamp/invoker.properties

@@ -0,0 +1 @@
+invoker.goals=${project.groupId}:${project.artifactId}:${project.version}:set -DnewVersion=2.0

src/it/it-set-019-outputTimestamp/pom.xml

@@ -0,0 +1,14 @@
+<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>localhost</groupId>
+  <artifactId>it-set-019</artifactId>
+  <version>1.0</version>
+  <packaging>pom</packaging>
+  <name>set</name>
+
+  <properties>
+    <project.build.outputTimestamp>10</project.build.outputTimestamp>
+  </properties>
+</project>

src/it/it-set-019-outputTimestamp/verify.groovy

@@ -0,0 +1,3 @@
+pom = new File( basedir, "pom.xml" ).text;
+
+assert pom =~ /<project.build.outputTimestamp>\d\d\d\d+<.project.build.outputTimestamp>/

src/main/java/org/codehaus/mojo/versions/SetMojo.java

@@ -21,14 +21,18 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.Date;
 import java.util.LinkedHashSet;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.SortedMap;
+import java.util.TimeZone;
 import java.util.TreeMap;
 import java.util.regex.Pattern;
 
@@ -485,6 +489,9 @@ protected synchronized void update( ModifiedPomXMLEventReader pom )
             for ( VersionChange versionChange : sourceChanges )
             {
                 changer.apply( versionChange );
+
+                // also update project.build.outputTimestamp
+                updateBuildOutputTimestamp( pom, model );
             }
         }
         catch ( IOException e )
@@ -494,4 +501,36 @@ protected synchronized void update( ModifiedPomXMLEventReader pom )
         log.clearContext();
     }
 
+    private void updateBuildOutputTimestamp( ModifiedPomXMLEventReader pom, Model model )
+        throws XMLStreamException
+    {
+        String buildOutputTimestamp = model.getProperties().getProperty( "project.build.outputTimestamp" );
+
+        if ( buildOutputTimestamp == null || StringUtils.isEmpty( buildOutputTimestamp ) )
+        {
+            // no Reproducible Builds output timestamp defined
+            return;
+        }
+
+        if ( StringUtils.isNumeric( buildOutputTimestamp ) )
+        {
+            // int representing seconds since the epoch, like SOURCE_DATE_EPOCH
+            buildOutputTimestamp = String.valueOf( System.currentTimeMillis() / 1000 );
+        }
+        else if ( buildOutputTimestamp.length() <= 1 )
+        {
+            // value length == 1 means disable Reproducible Builds
+            return;
+        }
+        else
+        {
+            // ISO-8601
+            DateFormat df = new SimpleDateFormat( "yyyy-MM-dd'T'HH:mm:ss'Z'" );
+            df.setTimeZone( TimeZone.getTimeZone( "UTC" ) );
+            buildOutputTimestamp = df.format( new Date() );
+        }
+
+        PomHelper.setPropertyVersion( pom, null, "project.build.outputTimestamp", buildOutputTimestamp );
+    }
+
 }