Symlinks aren't handled correctly

首先使用新的或修改后的符号链接重现问题，然后检查该工具的 commit blob 生成和文件模式处理。将生成的 commit 与预期的符号链接目标行为以及 qoomon/actions--create-commit 的成功结果进行比较。完成的标准是：该工具及其依赖的 action 创建或更新指向目标文件的符号链接，而不是将目标内容当作文件名处理。

Unsure if this should be here, or in the ghcommit-action repo. It appears likely there's an assumption being made about the file modes when generating the commit blobs. This causing this utility (and dependent action) to generate defunct commits.

Reproducer: Create a new, or modify an existing, symlink to file in the repo. Run the utility (or Github action).

Expected result: the symlink is created/updated to point to the target file.

Actual result: the symlink points to a non-existent file. The name of this file is the contents of the symlink target.

As I'm able to use another action achieve a similar result successfully (qoomon/actions--create-commit), I presume this isn't a limitation of the GH API, but something specific to its usage here.