JENKINS-58313 Add source commit and branch name

pom.xml

@@ -98,7 +98,7 @@
             <groupId>org.jenkins-ci.plugins</groupId>
             <artifactId>branch-api</artifactId>
             <version>2.1.2</version>
-            <scope>test</scope>
+            <optional>true</optional>
         </dependency>
         <dependency>
             <groupId>org.jenkins-ci.plugins</groupId>

src/main/java/org/jenkinsci/plugins/github_branch_source/GitHubEnvContributor.java

@@ -0,0 +1,79 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2019 Tim Jacomb
+ *
+ * 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 org.jenkinsci.plugins.github_branch_source;
+
+import hudson.EnvVars;
+import hudson.Extension;
+import hudson.model.EnvironmentContributor;
+import hudson.model.ItemGroup;
+import hudson.model.Job;
+import hudson.model.TaskListener;
+import java.util.HashMap;
+import java.util.Map;
+import javax.annotation.Nonnull;
+import jenkins.branch.BranchProjectFactory;
+import jenkins.branch.MultiBranchProject;
+import jenkins.plugins.git.AbstractGitSCMSource;
+import jenkins.scm.api.SCMRevision;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
+
+@Extension(optional = true)
+@Restricted(NoExternalUse.class)
+public class GitHubEnvContributor extends EnvironmentContributor {
+
+    private static final String CHANGE_SOURCE_COMMIT_ID = "CHANGE_SOURCE_COMMIT_ID";
+    private static final String CHANGE_MERGE_COMMIT_ID = "CHANGE_MERGE_COMMIT_ID";
+    private static final String CHANGE_BASE_COMMIT_ID = "CHANGE_BASE_COMMIT_ID";
+    private static final String CHANGE_BRANCH = "CHANGE_BRANCH";
+
+    @SuppressWarnings("unchecked")
+    public void buildEnvironmentFor(Job job, @Nonnull EnvVars envs, @Nonnull TaskListener listener) {
+        ItemGroup parent = job.getParent();
+        if (parent instanceof MultiBranchProject) {
+            BranchProjectFactory projectFactory = ((MultiBranchProject) parent).getProjectFactory();
+            SCMRevision revision = projectFactory.getRevision(job);
+
+            Map<String, String> envValues = new HashMap<>();
+            if (revision instanceof PullRequestSCMRevision) {
+                PullRequestSCMRevision pullRequestSCMRevision = (PullRequestSCMRevision) revision;
+
+                envValues.put(CHANGE_SOURCE_COMMIT_ID, pullRequestSCMRevision.getPullHash());
+                envValues.put(CHANGE_MERGE_COMMIT_ID, pullRequestSCMRevision.getMergeHash());
+                envValues.put(CHANGE_BASE_COMMIT_ID, pullRequestSCMRevision.getBaseHash());
+
+
+            } else if (revision instanceof AbstractGitSCMSource.SCMRevisionImpl) {
+                AbstractGitSCMSource.SCMRevisionImpl gitRevision = (AbstractGitSCMSource.SCMRevisionImpl) revision;
+
+                envValues.put(CHANGE_SOURCE_COMMIT_ID, gitRevision.getHash());
+                envValues.put(CHANGE_BRANCH, revision.getHead().getName());
+
+            } else {
+                throw new IllegalArgumentException("did not recognize " + revision);
+            }
+            envs.putAll(envValues);
+        }
+    }
+}