feat(commits): add commit pull request lookup

Co-Authored-By: Virgil <virgil@lethean.io>

commits.go

@@ -53,6 +53,21 @@ func (s *CommitService) Get(ctx context.Context, params Params) (*types.Commit,
 	return &out, nil
 }
 
+// GetPullRequest returns the pull request associated with a commit SHA.
+//
+// Usage:
+//
+//	f := forge.NewForge("https://forge.lthn.ai", "token")
+//	_, err := f.Commits.GetPullRequest(ctx, "core", "go-forge", "abc123")
+func (s *CommitService) GetPullRequest(ctx context.Context, owner, repo, sha string) (*types.PullRequest, error) {
+	path := ResolvePath("/api/v1/repos/{owner}/{repo}/commits/{sha}/pull", pathParams("owner", owner, "repo", repo, "sha", sha))
+	var out types.PullRequest
+	if err := s.client.Get(ctx, path, &out); err != nil {
+		return nil, err
+	}
+	return &out, nil
+}
+
 // GetCombinedStatus returns the combined status for a given ref (branch, tag, or SHA).
 func (s *CommitService) GetCombinedStatus(ctx context.Context, owner, repo, ref string) (*types.CombinedStatus, error) {
 	path := ResolvePath("/api/v1/repos/{owner}/{repo}/statuses/{ref}", pathParams("owner", owner, "repo", repo, "ref", ref))

commits_test.go

@@ -95,6 +95,41 @@ func TestCommitService_Get_Good(t *testing.T) {
 	}
 }
 
+func TestCommitService_GetPullRequest_Good(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			t.Errorf("expected GET, got %s", r.Method)
+		}
+		if r.URL.Path != "/api/v1/repos/core/go-forge/commits/abc123/pull" {
+			t.Errorf("wrong path: %s", r.URL.Path)
+		}
+		json.NewEncoder(w).Encode(types.PullRequest{
+			ID:    17,
+			Index: 9,
+			Title: "Add commit-linked pull request",
+			Head: &types.PRBranchInfo{
+				Ref: "feature/commit-link",
+			},
+		})
+	}))
+	defer srv.Close()
+
+	f := NewForge(srv.URL, "tok")
+	pr, err := f.Commits.GetPullRequest(context.Background(), "core", "go-forge", "abc123")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if pr.ID != 17 {
+		t.Errorf("got id=%d, want 17", pr.ID)
+	}
+	if pr.Index != 9 {
+		t.Errorf("got index=%d, want 9", pr.Index)
+	}
+	if pr.Head == nil || pr.Head.Ref != "feature/commit-link" {
+		t.Fatalf("unexpected head branch info: %+v", pr.Head)
+	}
+}
+
 func TestCommitService_ListStatuses_Good(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodGet {