Re-write link to perma link

[jixunmoe]

I was experimenting with custom slug for tags (permalink), and it does not work out-of-the-box.

For both language, it contains the following post meta:

tags = [
    "闲聊",    # chit chat
    "不存在",  # non-exist (to test fallback when custom meta file does not exist)
]

As my initial investigation, I've found that you can get the permalink to a tag in this rather verbose way:

<!-- post-info.html, tags rendering -->
                    {{ range $tag_name := .Params.tags }}
                        {{ $tag := ($.Site.GetPage (printf "/tags/%s" $tag_name)) }}
                        <li><a href="{{ $tag.Permalink }}">#{{ $tag.Title | default $tag_name }}</a></li>
                    {{ end }}

Which manages to render the correct url for both language:

<!-- en -->
<ul class="post-tags">
                        <li><a href="http://localhost:1313/en/tags/custom-tag/">#Custom title</a></li>
                        <li><a href="http://localhost:1313/en/tags/%E4%B8%8D%E5%AD%98%E5%9C%A8/">#不存在</a></li>
                </ul>

<!-- zh-cn: default -->

<ul class="post-tags">
                        <li><a href="http://localhost:1313/tags/chitchat/">#闲聊</a></li>
                        <li><a href="http://localhost:1313/tags/%E4%B8%8D%E5%AD%98%E5%9C%A8/">#不存在</a></li>
                </ul>

Is getting late now, so I've just documented the discovery I had. I can do a PR later if required.

PR already created in #133

Reproduce

First config custom permalinks:

# config.toml

[permalinks]
tags = "/tags/:slug/" # set to "/silly-tags/:slug/" also works :D

And define mapping like so:

<!-- file: content/tags/闲聊/_index.md -->
+++
# title is missing for native language, which should fallback to its key "闲聊"
slug = "chitchat"
+++


<!-- file: content/tags/闲聊/_index.en.md -->
+++
title = "Custom title"
slug = "custom-tag" # if this field is missing, it will be derived from title instead of inherit from native language...
+++

[jixunmoe]

closed in #133