Add body option to gitalk configuration to support custom issue content (#877)

Co-authored-by: Mimi <1119186082@qq.com>

_config.yml

@@ -733,6 +733,10 @@ gitalk:
   # If you want everyone visiting your site to see a uniform language, you can set a force language value
   # Available values: en | es-ES | fr | ru | zh-CN | zh-TW
   language:
+  # If you want to customize the content of the initialized Issue, please edit the body parameter.
+  # For example:
+  # body: Comments for post ${title}, see ${url}
+  body:
 
 # Utterances
 # For more information: https://utteranc.es

source/js/third-party/comments/gitalk.js

@@ -3,6 +3,20 @@
 document.addEventListener('page:loaded', async () => {
   if (!CONFIG.page.comments) return;
 
+  // Parse and replace body expressions
+  const allowed = {
+    title: document.title,
+    url  : location.href,
+    path : location.pathname,
+    lang : navigator.language
+  };
+
+  const parsedBody = CONFIG.gitalk.body?.replace(/\$\{([^}]+)}/g, (_, keyRaw) => {
+    const key = keyRaw.trim();
+    if (!/^[A-Za-z0-9_]+$/.test(key)) return '';
+    return String(allowed[key] ?? '');
+  });
+
   await NexT.utils.loadComments('.gitalk-container');
   await NexT.utils.getScript(CONFIG.gitalk.js, {
     condition: window.Gitalk
@@ -16,7 +30,8 @@ document.addEventListener('page:loaded', async () => {
     id                 : CONFIG.gitalk.path_md5,
     proxy              : CONFIG.gitalk.proxy,
     language           : CONFIG.gitalk.language || window.navigator.language,
-    distractionFreeMode: CONFIG.gitalk.distraction_free_mode
+    distractionFreeMode: CONFIG.gitalk.distraction_free_mode,
+    body               : parsedBody
   });
   gitalk.render(document.querySelector('.gitalk-container'));
 });