Restore legacy permalink behavior using :filepath pattern

[dimaslanjaka]

What does it do?

This PR introduces or adjusts the :filepath permalink pattern to replicate the previous behavior of :title, which was based on the post's file name and path under source/_posts/.

✅ What this PR does:

• Restores old permalink behavior via :filepath
• Enables backward compatibility for existing blogs without requiring manual changes to thousands of posts
• Preserves legacy URLs and helps prevent SEO regressions or broken external links

🧪 How to test:

1. Add the following to your _config.yml:

   permalink: :filepath/

2. Make sure your posts inside source/_posts/ generate the expected permalinks matching the file name.

📌 Related Issue / Discussion:

• Original issue and discussion

• Issue describing permalink regression

🙏 Note:

This change helps long-time users maintain their blog structure and avoid unnecessary mass edits due to the breaking permalink change. Especially for blogger/wordpress users who have migrated to Hexo.

🔍 Test Results:

• Dev repo (Hexo fork):
  https://github.com/dimaslanjaka/hexo/tree/603a01549d895b60994e7b455574c5c915b4e35c

• Test unit repo:
  https://github.com/dimaslanjaka/hexo-theme-unit-test/tree/monorepo

• Test result output (gh-pages):
  https://github.com/dimaslanjaka/hexo-theme-unit-test/tree/gh-pages

• Live site preview:
  https://www.webmanajemen.com/hexo-theme-unit-test/

All posts render with the expected permalink structure using the :filepath pattern.

Screenshots

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

[github-actions]

How to test

git clone -b filepath-permalink https://github.com/dimaslanjaka/hexo.git
cd hexo
npm install
npm test