Add support for MergeMethod on GHPullRequest

src/main/java/org/kohsuke/github/GHPullRequest.java

@@ -277,7 +277,7 @@ public GHPullRequestReviewComment createReviewComment(String body, String sha, S
      *      Commit message. If null, the default one will be used.
      */
     public void merge(String msg) throws IOException {
-        merge(msg,null);
+        merge(msg,(String)null);
     }
 
     /**
@@ -294,6 +294,25 @@ public void merge(String msg, String sha) throws IOException {
         new Requester(root).method("PUT").with("commit_message",msg).with("sha",sha).to(getApiRoute()+"/merge");
     }
 
+    /**
+     * Merge this pull request, using the specified merge method.
+     *
+     * The equivalent of the big green "Merge pull request" button.
+     *
+     * @param msg
+     *      Commit message. If null, the default one will be used.
+     * @param method
+     *      SHA that pull request head must match to allow merge.
+     */
+    public void merge(String msg, MergeMethod method) throws IOException {
+        new Requester(root).method("PUT")
+		.with("commit_message",msg)
+		.with("merge_method",method)
+		.to(getApiRoute()+"/merge");
+    }
+
+    public enum MergeMethod{ MERGE, SQUASH, REBASE }
+
     private void fetchIssue() throws IOException {
         if (!fetchedIssueDetails) {
             new Requester(root).to(getIssuesApiRoute(), this);

src/main/java/org/kohsuke/github/Previews.java

@@ -8,4 +8,5 @@
     static final String DRAX = "application/vnd.github.drax-preview+json";
     static final String SQUIRREL_GIRL = "application/vnd.github.squirrel-girl-preview";
     static final String KORRA = "application/vnd.github.korra-preview";
+    static final String POLARIS = "application/vnd.github.polaris-preview";
 }

src/test/java/org/kohsuke/github/PullRequestTest.java

@@ -69,6 +69,19 @@ public void testMergeCommitSHA() throws Exception {
         fail();
     }
 
+    @Test
+    public void testSquashMerge() throws Exception {
+        String name = rnd.next();
+        GHRef masterRef = getRepository().getRef("heads/master");
+        GHRef branchRef = getRepository().createRef("refs/heads/" + name, masterRef.getObject().getSha());
+        getRepository().createContent(name, name, name, name);
+        Thread.sleep(1000);
+        GHPullRequest p = getRepository().createPullRequest(name, name, "master", "## test squash");
+        Thread.sleep(1000);
+        p.merge("squash merge", GHPullRequest.MergeMethod.SQUASH);
+        branchRef.delete();
+    }
+
     @Test
     // Requires push access to the test repo to pass
     public void setLabels() throws Exception {