Added a new extension point to contribute build variables.

changelog.html

@@ -113,6 +113,8 @@ Upcoming changes</a>
     (<a href="http://issues.jenkins-ci.org/browse/JENKINS-7743">issue 7743</a>)
   <li class=rfe>
     LDAP group names are now available as-is for the use in authorization. No upper casing / no 'ROLE_' prefix.
+  <li class=rfe>
+    Added a new extension point to contribute build variables.
 </ul>
 </div><!--=TRUNK-END=-->
 

core/src/main/java/hudson/model/AbstractBuild.java

@@ -827,6 +827,9 @@ public abstract class AbstractBuild<P extends AbstractProject<P,R>,R extends Abs
                 bw.makeBuildVariables(this,r);
         }
 
+        for (BuildVariableContributor bvc : BuildVariableContributor.all())
+            bvc.buildVariablesFor(this,r);
+
         return r;
     }
 

core/src/main/java/hudson/model/BuildVariableContributor.java

+/*
+ * The MIT License
+ *
+ * Copyright (c) 2010, CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package hudson.model;
+
+import hudson.ExtensionList;
+import hudson.ExtensionPoint;
+import hudson.tasks.Builder;
+import hudson.tasks.Publisher;
+
+import java.util.Map;
+
+/**
+ * Contributes build variables to builds.
+ *
+ * <p>
+ * This extension point can be used to externally add build variables, which are then used for
+ * various parameter expansions by {@link Builder}s and {@link Publisher}s. Aside from adding variables
+ * of the fixed name, a typical strategy is to look for specific {@link JobProperty}s and other similar configurations
+ * of {@link Job}s to compute values.
+ *
+ * @author Kohsuke Kawaguchi
+ * @since 1.403
+ * @see EnvironmentContributor
+ */
+public abstract class BuildVariableContributor implements ExtensionPoint {
+    /**
+     * Contributes build variables used for a build.
+     *
+     * <p>
+     * This method can be called repeatedly for the same {@link AbstractBuild}, thus
+     * the computation of this method needs to be efficient. If you have a time-consuming
+     * computation, one strategy is to take the hit once and then add the result as {@link InvisibleAction}
+     * to {@link AbstractBuild}, then reuse those values later on.
+     *
+     * <p>
+     * This method gets invoked concurrently for multiple {@link Run}s that are being built at the same time,
+     * so it must be concurrent-safe.
+     *
+     * @param build
+     *      Build that's being performed. Never null.
+     * @param variables
+     *      Partially built variable map. Implementation of this method is expected to
+     *      add additional variables here. Never null.
+     */
+    public abstract void buildVariablesFor(AbstractBuild build, Map<String,String> variables);
+
+    /**
+     * Returns all the registered {@link EnvironmentContributor}s.
+     */
+    public static ExtensionList<BuildVariableContributor> all() {
+        return Hudson.getInstance().getExtensionList(BuildVariableContributor.class);
+    }
+}

core/src/main/java/hudson/model/EnvironmentContributor.java

@@ -39,6 +39,7 @@ import java.io.IOException;
  *
  * @author Kohsuke Kawaguchi
  * @since 1.392
+ * @see BuildVariableContributor
  */
 public abstract class EnvironmentContributor implements ExtensionPoint {
     /**