Fetch and cache file data from bintray, rename/introduce env variables...

Fetch and cache file data from bintray, rename/introduce env variables BINTRAY_USERNAME and BINTRAY_API_KEY

.gitignore

+_cache

index.php

 <?php
-$api_url = 'https://bauerj:' . getenv('API_KEY') . '@api.bintray.com/packages/borg-binary-builder/borg-binaries/borg-binaries/files';
-$_files  = file_get_contents($api_url);
-$_files  = json_decode($_files, false);
+
+function get_bintray_files_cache($force = false)
+{
+    $cache_file    = '_cache/bintray-files.json';
+    $cache_time    = 300;
+    $cache_expired = !file_exists($cache_file) || (time() - filemtime($cache_file) >= $cache_time);
+
+    if ($force || $cache_expired) {
+        $files_json = file_get_contents(sprintf(
+            'https://%s:%s@api.bintray.com/packages/borg-binary-builder/borg-binaries/borg-binaries/files',
+            getenv('BINTRAY_USERNAME'),
+            getenv('BINTRAY_API_KEY')
+        ));
+
+        file_put_contents($cache_file, $files_json);
+    } else {
+        $files_json = file_get_contents($cache_file);
+    }
+
+    return json_decode($files_json, false);
+}
 
 function human_filesize($bytes, $decimals = 2)
 {
@@ -24,7 +42,7 @@ function get_dl_link($flavor, $version, $file = null)
 }
 
 $files = [];
-foreach ($_files as $file) {
+foreach (get_bintray_files_cache() as $file) {
     $files[$file->name] = $file;
 }
 uasort($files, static function ($a, $b) {