Add auto-merge setting and merge now functionality

cache.go

@@ -164,6 +164,28 @@ func (c *CachedGitHubService) UpdatePullRequest(
 	return writer.UpdatePullRequest(ctx, pullRequestID, update)
 }
 
+func (c *CachedGitHubService) SetPullRequestAutoMerge(
+	ctx context.Context, pullRequestID, expectedHeadOID, mergeMethod string, enabled bool,
+) (*AutoMergeRequest, error) {
+	writer, ok := c.remote.(GitHubMergeService)
+	if !ok {
+		return nil, errors.New("GitHub service does not support auto-merge")
+	}
+	return writer.SetPullRequestAutoMerge(
+		ctx, pullRequestID, expectedHeadOID, mergeMethod, enabled,
+	)
+}
+
+func (c *CachedGitHubService) MergePullRequest(
+	ctx context.Context, pullRequestID, expectedHeadOID, mergeMethod string,
+) (PullRequestMergeResult, error) {
+	writer, ok := c.remote.(GitHubMergeService)
+	if !ok {
+		return PullRequestMergeResult{}, errors.New("GitHub service does not support merging")
+	}
+	return writer.MergePullRequest(ctx, pullRequestID, expectedHeadOID, mergeMethod)
+}
+
 func (c *CachedGitHubService) ListBranches(
 	ctx context.Context, owner, repo string,
 ) ([]RepositoryBranch, error) {