Labels as environment variable (#207)

* Add pull request labels as an environment variable. The contents will be a comma-separated string of all the labels

* Add line in documentation to mention the labels environment variable

* Style fix

Author: andreitroiebbc

docs/Configuration.adoc

@@ -45,6 +45,7 @@ like `Build #${BUILD_NUMBER} started`
 - `GITHUB_PR_STATE` - `OPEN`
 - `GITHUB_PR_COMMENT_BODY` - `test foo, bar tags please.` When PR was triggered by comment.
 - `GITHUB_PR_COMMENT_BODY_MATCH` - `foo, bar` When PR wass triggered by comment and had group match.
+- `GITHUB_PR_LABELS` - `label1,label2` Comma-separated list of labels that the PR has. Empty if the PR has no labels.
 
 === Branch Trigger
 

github-pullrequest-plugin/src/main/java/org/jenkinsci/plugins/github/pullrequest/data/GitHubPREnv.java

@@ -29,7 +29,8 @@ public enum GitHubPREnv {
     NUMBER,
     STATE,
     COMMENT_BODY,
-    COMMENT_BODY_MATCH;
+    COMMENT_BODY_MATCH,
+    LABELS;
 
     public static final String PREFIX = "GITHUB_PR_";
 

github-pullrequest-plugin/src/main/java/org/jenkinsci/plugins/github/pullrequest/trigger/JobRunnerForCause.java

@@ -52,6 +52,7 @@
 import static org.jenkinsci.plugins.github.pullrequest.data.GitHubPREnv.COND_REF;
 import static org.jenkinsci.plugins.github.pullrequest.data.GitHubPREnv.BODY;
 import static org.jenkinsci.plugins.github.pullrequest.data.GitHubPREnv.HEAD_SHA;
+import static org.jenkinsci.plugins.github.pullrequest.data.GitHubPREnv.LABELS;
 import static org.jenkinsci.plugins.github.pullrequest.data.GitHubPREnv.NUMBER;
 import static org.jenkinsci.plugins.github.pullrequest.data.GitHubPREnv.SHORT_DESC;
 import static org.jenkinsci.plugins.github.pullrequest.data.GitHubPREnv.SOURCE_BRANCH;
@@ -289,7 +290,8 @@ public QueueTaskFuture<?> startJob(GitHubPRCause cause, Cause additionalCause) {
                 NUMBER.param(String.valueOf(cause.getNumber())),
                 STATE.param(String.valueOf(cause.getState())),
                 COMMENT_BODY.param(String.valueOf(cause.getCommentBody())),
-                COMMENT_BODY_MATCH.param(String.valueOf(cause.getCommentBodyMatch()))
+                COMMENT_BODY_MATCH.param(String.valueOf(cause.getCommentBodyMatch())),
+                LABELS.param(String.join(",", cause.getLabels()))
         );
         parameters.addAll(pluginParameters);