Slice 10: create_pr (open a pull request)

forge CreatePullRequest (Gitea; empty base resolves to the repo default branch). Service CreatePR records a pr-created event. HTTP POST /api/repo/pr/create; MCP tool create_pr; <pr-list> New pull request button (head = selected repo current branch, base = default). Live-tested end-to-end: app create_pr opened a real PR (base auto-resolved), listed, then cleaned up; main untouched.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/forge/forge.go

@@ -48,11 +48,21 @@ type MergeResult struct {
 	BranchDeleted bool   `json:"branchDeleted"`
 }
 
+// NewPR describes a pull request to open. An empty Base means "the repo's
+// default branch".
+type NewPR struct {
+	Head  string
+	Base  string
+	Title string
+	Body  string
+}
+
 // Provider talks to one hosting provider.
 type Provider interface {
 	// Handles reports whether this provider serves the given remote host.
 	Handles(host string) bool
 	ListPullRequests(ctx context.Context, owner, repo string) ([]PullRequest, error)
+	CreatePullRequest(ctx context.Context, owner, repo string, pr NewPR) (PullRequest, error)
 	MergeAndCleanup(ctx context.Context, owner, repo string, number int64, method MergeMethod) (MergeResult, error)
 }
 

internal/forge/gitea.go

@@ -54,6 +54,36 @@ func (g *Gitea) ListPullRequests(_ context.Context, owner, repo string) ([]PullR
 	return out, nil
 }
 
+// CreatePullRequest opens a PR. An empty Base resolves to the repo's default
+// branch. Requires the head branch to already exist on the remote.
+func (g *Gitea) CreatePullRequest(_ context.Context, owner, repo string, pr NewPR) (PullRequest, error) {
+	if strings.TrimSpace(pr.Head) == "" {
+		return PullRequest{}, fmt.Errorf("a head branch is required")
+	}
+	base := strings.TrimSpace(pr.Base)
+	if base == "" {
+		r, _, err := g.client.GetRepo(owner, repo)
+		if err != nil {
+			return PullRequest{}, err
+		}
+		base = r.DefaultBranch
+	}
+	title := pr.Title
+	if strings.TrimSpace(title) == "" {
+		title = pr.Head
+	}
+	created, _, err := g.client.CreatePullRequest(owner, repo, gitea.CreatePullRequestOption{
+		Head:  pr.Head,
+		Base:  base,
+		Title: title,
+		Body:  pr.Body,
+	})
+	if err != nil {
+		return PullRequest{}, err
+	}
+	return toPR(created), nil
+}
+
 // MergeAndCleanup merges the PR and deletes its head branch (when the head is in
 // the same repo — never a fork's branch). Callers MUST have confirmed with the
 // user first (§1.4).