From c2d640f46a85785d5f16ad12cdb9770b27571f74 Mon Sep 17 00:00:00 2001
From: Aleksandr Mashchenko <aleksandr.7m@gmail.com>
Date: Fri, 19 Mar 2021 23:03:42 +0200
Subject: [PATCH] Update project.build.outputTimestamp property to support
 reproducible builds - closes #286

---
 .../plugin/gitflow/AbstractGitFlowMojo.java   | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/src/main/java/com/amashchenko/maven/plugin/gitflow/AbstractGitFlowMojo.java b/src/main/java/com/amashchenko/maven/plugin/gitflow/AbstractGitFlowMojo.java
index 8de164d5..24f1ff86 100644
--- a/src/main/java/com/amashchenko/maven/plugin/gitflow/AbstractGitFlowMojo.java
+++ b/src/main/java/com/amashchenko/maven/plugin/gitflow/AbstractGitFlowMojo.java
@@ -15,10 +15,14 @@
  */
 package com.amashchenko.maven.plugin.gitflow;
 
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
 import java.util.ArrayList;
+import java.util.Date;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.TimeZone;
 import java.util.regex.Pattern;
 
 import org.apache.maven.artifact.ArtifactUtils;
@@ -49,6 +53,8 @@ public abstract class AbstractGitFlowMojo extends AbstractMojo {
     private static final String VERSIONS_MAVEN_PLUGIN_SET_PROPERTY_GOAL = "org.codehaus.mojo:versions-maven-plugin:set-property";
     /** Name of the tycho-versions-plugin set-version goal. */
     private static final String TYCHO_VERSIONS_PLUGIN_SET_GOAL = "org.eclipse.tycho:tycho-versions-plugin:set-version";
+    /** Name of the property needed to have reproducible builds. */
+    private static final String REPRODUCIBLE_BUILDS_PROPERTY = "project.build.outputTimestamp";
 
     /** System line separator. */
     protected static final String LS = System.getProperty("line.separator");
@@ -245,6 +251,18 @@ protected String getCurrentProjectVersion() throws MojoFailureException {
         return reloadedProject.getVersion();
     }
 
+    /**
+     * Gets current project {@link #REPRODUCIBLE_BUILDS_PROPERTY} property value
+     * from pom.xml file.
+     * 
+     * @return Value of {@link #REPRODUCIBLE_BUILDS_PROPERTY} property.
+     * @throws MojoFailureException
+     */
+    private String getCurrentProjectOutputTimestamp() throws MojoFailureException {
+        final MavenProject reloadedProject = reloadProject(mavenSession.getCurrentProject());
+        return reloadedProject.getProperties().getProperty(REPRODUCIBLE_BUILDS_PROPERTY);
+    }
+
     /**
      * Reloads project info from file
      * 
@@ -1037,6 +1055,24 @@ protected void mvnSetVersions(final String version) throws MojoFailureException,
             }
             if (runCommand) {
                 executeMvnCommand(args.toArray(new String[0]));
+
+                String timestamp = getCurrentProjectOutputTimestamp();
+                if (timestamp != null && timestamp.length() > 1) {
+                    if (StringUtils.isNumeric(timestamp)) {
+                        // int representing seconds since the epoch
+                        timestamp = String.valueOf(System.currentTimeMillis() / 1000l);
+                    } else {
+                        // ISO-8601
+                        DateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
+                        df.setTimeZone(TimeZone.getTimeZone("UTC"));
+                        timestamp = df.format(new Date());
+                    }
+
+                    getLog().info("Updating property '" + REPRODUCIBLE_BUILDS_PROPERTY + "' to '" + timestamp + "'.");
+
+                    executeMvnCommand(VERSIONS_MAVEN_PLUGIN_SET_PROPERTY_GOAL, "-DgenerateBackupPoms=false",
+                            "-Dproperty=" + REPRODUCIBLE_BUILDS_PROPERTY, "-DnewVersion=" + timestamp);
+                }
             }
         }
     }