Add new filter type theme_inject

[jiangtj]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines.
• Tests for the changes was maked (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
• Docs in NexT website have been added / updated (for new features).

PR Type

What kind of change does this PR introduce?

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe:

What is the current behavior?

Through update custom layout file.

Issue resolved: N/A

What is the new behavior?

Inject custom layout.

I want to write an new theme by myself, based on NexT.
This is a core feature, and want to refactor comment post_meta etc, based on it.

• Link to demo site with this changes:
  • a plugin: https://github.com/jiangtj-lab/hexo-cake-moon-menu
  • complex config: https://gitlab.com/JiangTJ/next-test/blob/master/scripts/moon-menu-for-muse-mist.js

How to use?

For advanced-settings user, you can write code as following. And others can see Breaking Change, if you have compatibility issue.

In scripts:

hexo.extend.filter.register('theme_inject', function(injects) {
  injects.head.file('custom-name', 'source/_data/head.swig', {}, {cache: true});
  injects.sidebar.raw('custom-name', 'Put some in sidebar!');
});

Layout (point: ['head', 'header', 'sidebar', 'postMeta', 'postBodyEnd', 'footer', 'bodyEnd'] )

• injects.[point].file(name, filePath, [locals], [options]);
• injects.[point].raw(name, raw, [locals], [options]);

Style (point: ['variable', 'mixin', 'style'] )

• injects.[point].push(styleFile)

Does this PR introduce a breaking change?

• Yes.
• No.

Breaking Change

Remove default custom layout files (layout/_custom/*) and css files.

If you define the content in the default custom layout files, you will need to migrate it into the hexo directory and define it in the custom_file_path.

Example: move theme source/css/_variables/custom.styl to hexo source/_data/variables.styl, and then config as following:

custom_file_path:
  variable: source/_data/variables.styl

DIFF:

- #custom_file_path:
+ custom_file_path:
-   # Default paths: layout/_custom/*
-   # Default path: source/css/_variables/custom.styl	
-   # Default path: source/css/_mixins/custom.styl	
-   # Default path: source/css/_custom/custom.styl
-   #variables: source/_data/variables.styl
-   #mixins: source/_data/mixins.styl	 
-   #styles: source/_data/styles.styl
+   #postMeta: source/_data/post-meta.swig
+   #postBodyEnd: source/_data/post-body-end.swig
+   #footer: source/_data/footer.swig
+   #bodyEnd: source/_data/body-end.swig
+   #variable: source/_data/variables.styl
+   #mixin: source/_data/mixins.styl 
+   #style: source/_data/styles.styl

[stevenjoezhang]

And docs here...

hexo-theme-next/source/css/_schemes/Gemini/index.styl

Line 19 in 89b8663

// P.S. If u want to change this paddings u may set this variables into `source/css/_variables/custom.styl`.

[jiangtj]

And docs here...

hexo-theme-next/source/css/_schemes/Gemini/index.styl

Line 19 in 89b8663

// P.S. If u want to change this paddings u may set this variables into `source/css/_variables/custom.styl`.

Why is there a doc here? QAQ

[stevenjoezhang]

// P.S. If u want to change this paddings u may set this variables into `source/css/_variables/custom.styl`. 

->

// P.S. If u want to change this paddings u may set this variables into `source/_data/variables.styl`. 

[stevenjoezhang]

And... how about a post-end inject point: #835

[jiangtj]

And... how about a post-end inject point: #835

Yeah 😂, In addition, we also can add post-mate after you refactored.