Summary

• Fix(*Worktree).Commit() panic whenCommitOptions parameter is nil
• Add test caseTestCommitWithNilOptions to verify the fix

Root Cause

When callingCommit() with a nilCommitOptions pointer, the function would immediately callopts.Validate() which causes a nil pointer dereference panic.

Solution

Check ifopts is nil before callingValidate(), and initialize it to an emptyCommitOptions{} struct. TheValidate() method already handles setting default values (Author from git config, Committer defaults to Author, Parents defaults to HEAD).

This follows the maintainer guidance from@pjbgf in the issue: "replacing nil to pointer to an empty struct" is fine when there's valid default options.

Test Plan

• AddedTestCommitWithNilOptions test case
• All existing tests pass (go test ./...)

Fixes#1051