title: What does "locked at" <tag> mean when running "composer update <package>"?
body: <p>I am trying to perform a <code>composer update &lt;package&gt;</code> but getting the following error:</p>
  <blockquote>
  <p>The requested package &lt;package&gt; (locked at &lt;tag&gt;, required as
  &lt;version&gt;) is satisfiable by &lt;package&gt;[&lt;tag&gt;] but these conflict
  with your requirements or minimum-stability.</p>
  </blockquote>
  <p>Meanwhile, the tag <code>&lt;tag&gt;</code> exists as a string only in my composer.lock file, which I thought was only modified by <code>composer update</code>, not read back.</p>
  <p>I tried running <code>composer why-not &lt;package&gt;</code>, but its output didn't really explain the issue:</p>
  <blockquote>
  <p>&lt;program&gt; &lt;other-version&gt; requires &lt;package&gt; (&lt;version&gt;)</p>
  </blockquote>
  <p>What does 'locked at' mean in this context and how do I solve the issue?</p>