Enable incrementals (#61)

https://www.jenkins.io/doc/developer/plugin-development/incrementals/

Preparing to enable CD

Author: MarkEWaite

.mvn/extensions.xml

@@ -0,0 +1,7 @@
+<extensions xmlns="http://maven.apache.org/EXTENSIONS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/EXTENSIONS/1.0.0 http://maven.apache.org/xsd/core-extensions-1.0.0.xsd">
+  <extension>
+    <groupId>io.jenkins.tools.incrementals</groupId>
+    <artifactId>git-changelist-maven-extension</artifactId>
+    <version>1.8</version>
+  </extension>
+</extensions>

.mvn/maven.config

@@ -0,0 +1,2 @@
+-Pconsume-incrementals
+-Pmight-produce-incrementals

pom.xml

@@ -9,20 +9,23 @@
 
   <artifactId>port-allocator</artifactId>
   <packaging>hpi</packaging>
-  <version>1.13-SNAPSHOT</version>
+  <version>${revision}${changelist}</version>
   <name>Jenkins Port Allocator Plug-in</name>
   <url>https://github.com/jenkinsci/port-allocator-plugin</url>
 
   <properties>
+    <revision>1.13</revision>
+    <changelist>-SNAPSHOT</changelist>
+    <gitHubRepo>jenkinsci/port-allocator-plugin</gitHubRepo>
     <jenkins.baseline>2.479</jenkins.baseline>
     <jenkins.version>${jenkins.baseline}.1</jenkins.version>
   </properties>
 
   <scm>
-    <connection>scm:git:https://github.com/jenkinsci/port-allocator-plugin.git</connection>
-    <developerConnection>scm:git:git@github.com:jenkinsci/port-allocator-plugin.git</developerConnection>
-    <url>https://github.com/jenkinsci/port-allocator-plugin</url>
-    <tag>HEAD</tag>
+    <connection>scm:git:https://github.com/${gitHubRepo}.git</connection>
+    <developerConnection>scm:git:git@github.com:${gitHubRepo}.git</developerConnection>
+    <url>https://github.com/${gitHubRepo}</url>
+    <tag>${scmTag}</tag>
   </scm>
 
     <repositories>