feat(repo): add rename_branch tool (#245)

Adds a native `rename_branch` write tool so MCP clients can rename branches without emulating it via create + delete.

Changes:
- Add `rename_branch` to the repository branch tools with `owner`, `repo`, `branch`, and `new_name` parameters.
- Call the Gitea SDK's `RenameRepoBranch` operation and propagate API errors.
- Add handler/registration tests and README tool table entries.

Closes https://gitea.com/gitea/gitea-mcp/issues/236

Assisted by Codet

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/245
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>

operation/repo/branch.go

@@ -2,6 +2,7 @@ package repo
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
 	"gitea.com/gitea/gitea-mcp/pkg/annotation"
@@ -21,6 +22,7 @@ const (
 	CreateBranchToolName = "create_branch"
 	DeleteBranchToolName = "delete_branch"
 	ListBranchesToolName = "list_branches"
+	RenameBranchToolName = "rename_branch"
 )
 
 var (
@@ -52,6 +54,16 @@ var (
 		tool.Number("page", tool.Description(params.PageDesc), tool.Default(1)),
 		tool.Number("per_page", tool.Description(params.PaginationDesc), tool.Default(30)),
 	)
+
+	RenameBranchTool = tool.NewDefinition(
+		RenameBranchToolName,
+		"Rename an existing branch in a repository.",
+		annotation.Write("Rename a branch"),
+		tool.String("owner", tool.Required(), tool.Description(params.OwnerDesc)),
+		tool.String("repo", tool.Required(), tool.Description(params.RepoDesc)),
+		tool.String("branch", tool.Required()),
+		tool.String("new_name", tool.Required()),
+	)
 )
 
 func init() {
@@ -67,6 +79,10 @@ func init() {
 		Tool:    ListBranchesTool,
 		Handler: ListBranchesFn,
 	})
+	BranchTool.RegisterWrite(tool.ServerTool{
+		Tool:    RenameBranchTool,
+		Handler: RenameBranchFn,
+	})
 }
 
 func CreateBranchFn(ctx context.Context, args map[string]any) (*mcp.CallToolResult, error) {
@@ -149,3 +165,36 @@ func ListBranchesFn(ctx context.Context, args map[string]any) (*mcp.CallToolResu
 
 	return to.TextResult(slimBranches(branches))
 }
+
+func RenameBranchFn(ctx context.Context, args map[string]any) (*mcp.CallToolResult, error) {
+	owner, err := params.GetString(args, "owner")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	repo, err := params.GetString(args, "repo")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	branch, err := params.GetString(args, "branch")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	newName, err := params.GetString(args, "new_name")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+
+	client, err := gitea.ClientFromContext(ctx)
+	if err != nil {
+		return to.ErrorResult(fmt.Errorf("get gitea client err: %v", err))
+	}
+	successful, _, err := client.Repositories.RenameRepoBranch(ctx, owner, repo, branch, gitea_sdk.RenameRepoBranchOption{Name: newName})
+	if err != nil {
+		return to.ErrorResult(fmt.Errorf("rename branch error: %v", err))
+	}
+	if !successful {
+		return to.ErrorResult(errors.New("rename branch error: unsuccessful"))
+	}
+
+	return to.TextResult("Branch renamed")
+}