feat: CreateBranch should auto-resolve branch name to commit SHA

provider/github.go

@@ -317,10 +317,21 @@ func (g *githubProvider) ListBranches(ctx context.Context, owner, repo string) (
 }
 
 func (g *githubProvider) CreateBranch(ctx context.Context, owner, repo, branch, ref string) (*PlatformBranch, error) {
+	sha := ref
+	if !isCommitSHA(ref) {
+		commits, err := g.ListCommits(ctx, owner, repo, ListCommitsOptions{Branch: ref, PerPage: 1})
+		if err != nil {
+			return nil, fmt.Errorf("failed to resolve ref %q to commit SHA: %w", ref, err)
+		}
+		if len(commits) == 0 {
+			return nil, fmt.Errorf("no commits found on ref %q", ref)
+		}
+		sha = commits[0].SHA
+	}
 	_, _, err := g.client.Git.CreateRef(ctx, owner, repo, &github.Reference{
 		Ref: github.String("refs/heads/" + branch),
 		Object: &github.GitObject{
-			SHA: github.String(ref),
+			SHA: github.String(sha),
 		},
 	})
 	if err != nil {

provider/github_test.go

@@ -560,6 +560,12 @@ func TestGitHub_DeleteNote(t *testing.T) {
 func TestGitHub_CreateBranch(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
+		if strings.Contains(r.URL.Path, "/commits") {
+			json.NewEncoder(w).Encode([]*github.RepositoryCommit{
+				{SHA: github.String("abc123def456abc123def456abc123def456abc1")},
+			})
+			return
+		}
 		json.NewEncoder(w).Encode(&github.Reference{Ref: github.String("refs/heads/new-branch"), Object: &github.GitObject{SHA: github.String("abc")}})
 	}))
 	defer srv.Close()
@@ -575,6 +581,24 @@ func TestGitHub_CreateBranch(t *testing.T) {
 	}
 }
 
+func TestGitHub_CreateBranch_WithSHA(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(&github.Reference{Ref: github.String("refs/heads/new-branch"), Object: &github.GitObject{SHA: github.String("abc")}})
+	}))
+	defer srv.Close()
+	client, _ := github.NewEnterpriseClient(srv.URL+"/api/v3", "", srv.Client())
+	p := &githubProvider{client: client, baseURL: srv.URL}
+
+	b, err := p.CreateBranch(context.Background(), "owner", "repo", "new-branch", "abc123def456abc123def456abc123def456abc1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if b.Name != "new-branch" {
+		t.Errorf("expected new-branch, got %s", b.Name)
+	}
+}
+
 func TestGitHub_GetCRDiff(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")

provider/util.go

@@ -1,10 +1,19 @@
 package provider
 
 import (
+	"encoding/hex"
 	"net/http"
 	"strconv"
 )
 
+func isCommitSHA(s string) bool {
+	if len(s) != 40 {
+		return false
+	}
+	_, err := hex.DecodeString(s)
+	return err == nil
+}
+
 func parseTotalCount(headers http.Header, fallback int) int {
 	for _, key := range []string{"X-Total-Count", "X-Total"} {
 		if v := headers.Get(key); v != "" {