feat: support "themeConfig.sidebar: 'auto'" (close: #552)

Author: ulivz

docs/default-theme-config/README.md

@@ -250,6 +250,30 @@ sidebar: auto
 ---
 ```
 
+You can also enable it in all pages by using config:
+
+``` js
+// .vuepress/config.js
+module.exports = {
+  themeConfig: {
+    sidebar: 'auto'
+  }
+}
+```
+
+In [multi-language](../guide/i18n.md) mode, you can also apply it to a specific locale:
+
+``` js
+// .vuepress/config.js
+module.exports = {
+  themeConfig: {
+     '/': {
+       sidebar: 'auto'
+     }
+  }
+}
+```
+
 ### Disabling the Sidebar
 
 You can disable the sidebar on a specific page with `YAML front matter`:

docs/zh/default-theme-config/README.md

@@ -247,6 +247,30 @@ sidebar: auto
 ---
 ```
 
+你也可以通过配置来在所有页面中启用它：
+
+``` js
+// .vuepress/config.js
+module.exports = {
+  themeConfig: {
+    sidebar: 'auto'
+  }
+}
+```
+
+在 [多语言](../guide/i18n.md) 模式下, 你也可以将其应用到某一特定的语言下：
+
+``` js
+// .vuepress/config.js
+module.exports = {
+  themeConfig: {
+     '/zh/': {
+       sidebar: 'auto'
+     }
+  }
+}
+```
+
 ### 禁用侧边栏
 
 你可以通过 `YAML front matter` 来禁用指定页面的侧边栏：

lib/default-theme/util.js

@@ -109,16 +109,17 @@ function resolvePath (relative, base, append) {
 }
 
 export function resolveSidebarItems (page, route, site, localePath) {
-  const pageSidebarConfig = page.frontmatter.sidebar
-  if (pageSidebarConfig === 'auto') {
-    return resolveHeaders(page)
-  }
   const { pages, themeConfig } = site
 
   const localeConfig = localePath && themeConfig.locales
     ? themeConfig.locales[localePath] || themeConfig
     : themeConfig
 
+  const pageSidebarConfig = page.frontmatter.sidebar || localeConfig.sidebar || themeConfig.sidebar
+  if (pageSidebarConfig === 'auto') {
+    return resolveHeaders(page)
+  }
+
   const sidebarConfig = localeConfig.sidebar || themeConfig.sidebar
   if (!sidebarConfig) {
     return []