Release

internal/github/github.go

@@ -94,3 +94,49 @@ func (c *Client) UpsertPRComment(ctx context.Context, prNumber int, body string)
 		&gh.IssueComment{Body: gh.Ptr(markedBody)})
 	return err
 }
+
+const prMarker = "<!-- stamp-release-pr -->"
+
+// UpsertPR creates or updates a release PR from head into base.
+// It identifies a previously-created PR by the hidden marker in the body.
+// Returns the PR number and the URL.
+func (c *Client) UpsertPR(ctx context.Context, head, base, title, body string) (int, string, error) {
+	markedBody := prMarker + "\n" + body
+
+	// Search open PRs from this head branch.
+	prs, _, err := c.client.PullRequests.List(ctx, c.owner, c.repo, &gh.PullRequestListOptions{
+		State: "open",
+		Head:  c.owner + ":" + head,
+		Base:  base,
+	})
+	if err != nil {
+		return 0, "", fmt.Errorf("listing pull requests: %w", err)
+	}
+
+	for _, pr := range prs {
+		if strings.Contains(pr.GetBody(), prMarker) {
+			// Update existing PR.
+			updated, _, err := c.client.PullRequests.Edit(ctx, c.owner, c.repo, pr.GetNumber(),
+				&gh.PullRequest{
+					Title: gh.Ptr(title),
+					Body:  gh.Ptr(markedBody),
+				})
+			if err != nil {
+				return 0, "", fmt.Errorf("updating pull request: %w", err)
+			}
+			return updated.GetNumber(), updated.GetHTMLURL(), nil
+		}
+	}
+
+	// Create new PR.
+	pr, _, err := c.client.PullRequests.Create(ctx, c.owner, c.repo, &gh.NewPullRequest{
+		Title: gh.Ptr(title),
+		Head:  gh.Ptr(head),
+		Base:  gh.Ptr(base),
+		Body:  gh.Ptr(markedBody),
+	})
+	if err != nil {
+		return 0, "", fmt.Errorf("creating pull request: %w", err)
+	}
+	return pr.GetNumber(), pr.GetHTMLURL(), nil
+}