Ensure LICENSE and NOTICE in sources.jar

Uses the standard maven source plugin instead
of rebuilding it with assembly.

pom.xml

@@ -356,7 +356,6 @@
         <version>${orekit.maven-assembly-plugin.version}</version>
         <configuration>
           <descriptors>
-            <descriptor>src/main/assembly/source-jar-assembly.xml</descriptor>
             <descriptor>src/main/assembly/source-distribution-assembly.xml</descriptor>
           </descriptors>
         </configuration>
@@ -397,6 +396,7 @@
               <goal>copy-resources</goal>
             </goals>
             <configuration>
+              <!-- Ensure LICENSE and NOTICE are shipped with binary jar -->
               <outputDirectory>${project.build.outputDirectory}/META-INF</outputDirectory>
               <resources>
                 <resource>
@@ -411,6 +411,33 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>build-helper-maven-plugin</artifactId>
+        <version>${orekit.build-helper-maven-plugin.version}</version>
+        <executions>
+          <execution>
+            <id>add-resource</id>
+            <phase>process-resources</phase>
+            <goals>
+              <goal>add-resource</goal>
+            </goals>
+            <configuration>
+              <!-- Ensure LICENSE and NOTICE are shipped with sources jar -->
+              <resources>
+                <resource>
+                  <directory>.</directory>
+                  <targetPath>META-INF</targetPath>
+                  <includes>
+                    <include>LICENSE.txt</include>
+                    <include>NOTICE.txt</include>
+                  </includes>
+                </resource>
+              </resources>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-clean-plugin</artifactId>

release-guide.md

@@ -191,6 +191,7 @@ checksums:
 - orekit-X.Y.jar
 - orekit-X.Y-sources.jar
 - orekit-X.Y-javadoc.jar
+- orekit-X.Y-sources.zip
 
 The signature and checksum files have similar names with added extensions `.asc`,
 `.md5` and `.sha1`.

src/main/assembly/source-jar-assembly.xml

-<assembly>
-  <id>sources</id>
-  <formats>
-    <format>jar</format>
-  </formats>
-  <includeBaseDirectory>false</includeBaseDirectory>
-  <fileSets>
-    <fileSet>
-      <includes>
-       <include>LICENSE.txt</include>
-       <include>NOTICE.txt</include>
-      </includes>
-      <outputDirectory>META-INF</outputDirectory>
-    </fileSet>
-    <fileSet>
-      <directory>src/main/java</directory>
-      <outputDirectory>.</outputDirectory>
-      <includes>
-        <include>**/*.java</include>
-      </includes>
-      <useDefaultExcludes>true</useDefaultExcludes>
-    </fileSet>
-  </fileSets>
-</assembly>