feat: Add functionality to update github_branch_default instead of forcing replacement

github/resource_github_branch.go

@@ -16,6 +16,7 @@
 	return &schema.Resource{
 		Create: resourceGithubBranchCreate,
 		Read:   resourceGithubBranchRead,
+		Update: resourceGithubBranchUpdate,
 		Delete: resourceGithubBranchDelete,
 		Importer: &schema.ResourceImporter{
 			State: resourceGithubBranchImport,
@@ -31,7 +32,6 @@
 			"branch": {
 				Type:        schema.TypeString,
 				Required:    true,
-				ForceNew:    true,
 				Description: "The repository branch to create.",
 			},
 			"source_branch": {
@@ -186,7 +186,30 @@
 	return nil
 }
 
-func resourceGithubBranchImport(d *schema.ResourceData, meta any) ([]*schema.ResourceData, error) {
+func resourceGithubBranchUpdate(d *schema.ResourceData, meta interface{}) error {
+	if !d.HasChange("branch") {
+		return resourceGithubBranchRead(d, meta)
+	}
+
+	ctx := context.WithValue(context.Background(), ctxId, d.Id())
+	client := meta.(*Owner).v3client
+	orgName := meta.(*Owner).name
+	repoName, oldBranchName, err := parseTwoPartID(d.Id(), "repository", "branch")
+	if err != nil {
+		return err
+	}
+	newBranchName := d.Get("branch").(string)
+
+	if _, _, err := client.Repositories.RenameBranch(ctx, orgName, repoName, oldBranchName, newBranchName); err != nil {
+		return fmt.Errorf("error renaming GitHub branch %s/%s (%s -> %s): %w", orgName, repoName, oldBranchName, newBranchName, err)
+	}
+
+	d.SetId(buildTwoPartID(repoName, newBranchName))
+
+	return resourceGithubBranchRead(d, meta)
+}
+
+func resourceGithubBranchImport(d *schema.ResourceData, meta interface{}) ([]*schema.ResourceData, error) {
 	repoName, branchName, err := parseTwoPartID(d.Id(), "repository", "branch")
 	if err != nil {
 		return nil, err

github/resource_github_branch_test.go

@@ -201,4 +201,62 @@ func TestAccGithubBranch(t *testing.T) {
 			testCase(t, organization)
 		})
 	})
+
+	t.Run("renames a branch without replacement", func(t *testing.T) {
+		initialConfig := fmt.Sprintf(`
+			resource "github_repository" "test" {
+			  name = "tf-acc-test-%[1]s"
+			  auto_init = true
+			}
+
+			resource "github_branch" "test" {
+			  repository = github_repository.test.id
+			  branch     = "initial"
+			}
+		`, randomID)
+
+		renamedConfig := fmt.Sprintf(`
+			resource "github_repository" "test" {
+			  name = "tf-acc-test-%[1]s"
+			  auto_init = true
+			}
+
+			resource "github_branch" "test" {
+			  repository = github_repository.test.id
+			  branch     = "renamed"
+			}
+		`, randomID)
+
+		testCase := func(t *testing.T, mode string) {
+			resource.Test(t, resource.TestCase{
+				PreCheck:  func() { skipUnlessMode(t, mode) },
+				Providers: testAccProviders,
+				Steps: []resource.TestStep{
+					{
+						Config: initialConfig,
+					},
+					{
+						Config: renamedConfig,
+						Check: resource.ComposeTestCheckFunc(
+							resource.TestCheckResourceAttr(
+								"github_branch.test", "branch", "renamed",
+							),
+						),
+					},
+				},
+			})
+		}
+
+		t.Run("with an anonymous account", func(t *testing.T) {
+			t.Skip("anonymous account not supported for this operation")
+		})
+
+		t.Run("with an individual account", func(t *testing.T) {
+			testCase(t, individual)
+		})
+
+		t.Run("with an organization account", func(t *testing.T) {
+			testCase(t, organization)
+		})
+	})
 }