Restore the use of manifest.txt as discussed

Resolve Git conflicts

pom.xml

@@ -32,12 +32,10 @@
 -->
 <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>net.sourceforge.plantuml</groupId>
   <artifactId>plantuml</artifactId>
   <version>1.2021.15-SNAPSHOT</version>
   <packaging>jar</packaging>
-
   <name>PlantUML</name>
   <description>
       PlantUML is a component that allows to quickly write :
@@ -50,13 +48,11 @@
         * object diagram
     </description>
   <url>https://plantuml.com</url>
-
   <parent>
     <groupId>org.sonatype.oss</groupId>
     <artifactId>oss-parent</artifactId>
     <version>7</version>
   </parent>
-
   <properties>
     <finalName>${project.artifactId}-${project.version}</finalName>
     <maven.compiler.source>1.7</maven.compiler.source>
@@ -65,7 +61,6 @@
     <maven.compiler.testTarget>1.8</maven.compiler.testTarget>
     <main.class>net.sourceforge.plantuml.Run</main.class>
   </properties>
-
   <dependencyManagement>
     <dependencies>
       <dependency>
@@ -77,8 +72,6 @@
       </dependency>
     </dependencies>
   </dependencyManagement>
-	
-	
   <dependencies>
     <dependency>
       <groupId>org.apache.ant</groupId>
@@ -104,7 +97,6 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
-
   <licenses>
     <license>
       <name>The GNU General Public License</name>
@@ -112,18 +104,15 @@
       <distribution>repo</distribution>
     </license>
   </licenses>
-
   <scm>
     <connection>scm:svn:svn://svn.code.sf.net/p/plantuml/code/trunk</connection>
     <developerConnection>scm:svn:https://svn.code.sf.net/p/plantuml/code/trunk</developerConnection>
     <url>svn://svn.code.sf.net/p/plantuml/code/trunk</url>
   </scm>
-
   <issueManagement>
     <system>Sourceforge</system>
     <url>http://sourceforge.net/tracker/?group_id=259736</url>
   </issueManagement>
-
   <developers>
     <developer>
       <id>arnaud.roques</id>
@@ -131,7 +120,6 @@
       <email>plantuml@gmail.com</email>
     </developer>
   </developers>
-
   <build>
     <finalName>${finalName}</finalName>
     <sourceDirectory>${project.basedir}/src</sourceDirectory>
@@ -203,18 +191,11 @@
         </executions>
       </plugin>
       <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-jar-plugin</artifactId>
         <version>3.2.0</version>
         <configuration>
           <archive>
-                        <manifest>
-                            <addClasspath>true</addClasspath>
-                            <useUniqueVersions>false</useUniqueVersions>
-                            <mainClass>${main.class}</mainClass>
-                            <addBuildEnvironmentEntries>true</addBuildEnvironmentEntries>
-                            <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
-                        </manifest>
+            <manifestFile>manifest.txt</manifestFile>
           </archive>
         </configuration>
       </plugin>
@@ -244,7 +225,6 @@
       </plugin>
     </plugins>
   </build>
-
   <profiles>
     <profile>
       <!--