title: Orgmode: how to filter the blocks to be tangle?
body: <p>In Orgmode, is there a way to <strong>tangle just the blocks in subtree matching (or not matching) a specific tag</strong>?</p>
  
  <p>For instance with the following code </p>
  
  <pre><code>* A
  #+BEGIN_SRC c
     printf("Not exported");
  #+END_SRC
  
  * B                :D:
  
  #+BEGIN_SRC c
    printf("Exported");
  #+END_SRC
  </code></pre>
  
  <p>exporting along tag <em>D</em>, the tangle C file will only contains <code>printf("Exported");</code></p>
  
  <p>I'm using <code>org-mode</code> to organise my emacs config, and my goal is to <em>derive different configs</em> from the master one <code>emacs-config.org</code>. (for instance a lightconfig by marking just the specific)</p>