title: Append org-agenda-files with files of another directory
body: <p>So i try to create a list of string in the form</p>
  <pre><code>&quot;a&quot; &quot;b&quot; &quot;c&quot;
  </code></pre>
  <p>This is a list of files which i want to pass to <code>org-agenda-files</code>
  As for now this looks like this</p>
  <pre><code>(setq org-agenda-files &quot;~/.tasks.org&quot;)
  </code></pre>
  <p>Now i need to add some files coming from a directory. i can get those with <code>directory-files-recursively &quot;~/orgroam/daily&quot; &quot;\\</code>[^.].*\.org\'&quot;<code>. this will return lets say </code>(&quot;~/b&quot; &quot;~/c&quot;)`.</p>
  <p>The problem comes when i try to concatenate the &quot;a&quot;. What i have tied so far is</p>
  <pre><code>(list &quot;~/.tasks.org&quot; (mapconcat #'identity (directory-files-recursively &quot;~/orgroam/daily&quot; &quot;\\`[^.].*\\.org\\'&quot;) &quot; &quot;))
  </code></pre>
  <p>and</p>
  <pre><code>(concat &quot;~/.tasks.org &quot; (mapconcat #'identity (directory-files-recursively &quot;~/orgroam/daily&quot; &quot;\\`[^.].*\\.org\\'&quot;) &quot; &quot;))
  </code></pre>
  <p>but this returns <code>&quot;a&quot; &quot;b c&quot;</code> and <code>&quot;a b c&quot;</code></p>
  <p>Another thing i tried out is to add the result of <code>directory-files-recursively</code> after the <code>(setq org-agenda-files '(&quot;~/.tasks.org&quot;))</code> using <code>add-to-list</code>. in this case i get <code>Wrong type argument: stringp, (&quot;~/orgroam/daily/2022-01-19.org&quot; &quot;~/orgroam/daily/2022-01-28.org&quot;....)</code></p>
  <p>Does anyone have a suggestion to achieve the desired output for <code>org-agenda-files</code>?</p>