Starting with Smarty 3.1.21 Composer has been configured to load the packages from github.

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*                                                                             *
*  NOTE: Because of this change you must clear your local composer cache with *
*                 the "composer clearcache" command                           *
*                                                                             *
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To get the latest stable version use
    "require": {
        "smarty/smarty": "~3.1"
    }
in your composer.json file.

To get the trunk version use
    "require": {
        "smarty/smarty": "~3.1@dev"
    }

The "smarty/smarty" package will start at libs/....   subfolder.

To retrieve the development and documentation folders add
    "require-dev": {
        "smarty/smarty-dev": "~3.1@dev"
    }

If you are using (include) the composer generated autoloader.php which is located
in the /vendor folder it is no longer needed to require the Smarty.class.php file.