Treat latest version as current version (#418)

If the site is versioned, and the latest version is displayed, the URL will not change. We need to let Algolia know this is the case.

lib/core/Site.js

@@ -30,7 +30,7 @@ class Site extends React.Component {
       this.props.config.url +
       this.props.config.baseUrl +
       (this.props.url || 'index.html');
-    let latestVersion;
+    let docsVersion = this.props.version || 'current';
 
     const highlightDefaultVersion = '9.12.0';
     const highlightConfig = this.props.config.highlight || {
@@ -39,7 +39,10 @@ class Site extends React.Component {
     };
     const highlightVersion = highlightConfig.version || highlightDefaultVersion;
     if (fs.existsSync(CWD + '/versions.json')) {
-      latestVersion = require(CWD + '/versions.json')[0];
+      const latestVersion = require(CWD + '/versions.json')[0];
+      if (docsVersion === latestVersion) {
+        docsVersion = 'current';
+      }
     }
 
     // We do not want a lang attribute for the html tag if we don't have a language set
@@ -122,7 +125,7 @@ class Site extends React.Component {
                 algoliaOptions: ${JSON.stringify(
                   this.props.config.algolia.algoliaOptions
                 )
-                  .replace('VERSION', this.props.version || latestVersion)
+                  .replace('VERSION', docsVersion)
                   .replace('LANGUAGE', this.props.language)}
               });
             `,