title: Get git commit details without "git" command
body: <p>First, I've seen and read <a href="https://stackoverflow.com/questions/3814926/git-commit-date">Git commit date</a>.</p>
  
  <p>How can I get the date of the current HEAD commit in git repo <em>without</em> execution any "git" command? Example: I'm execution commands from PHP and I cannot call <code>exec</code>, but I want to get current commit details.</p>
  
  <p>I have access to .git folder of this repo, but it doesn't seem to be useful for commit details. I was only able to get:</p>
  
  <ul>
  <li>Current branch from <code>.git/HEAD</code></li>
  <li>Current commit id (SHA) from <code>.git/refs/heads/&lt;branch&gt;</code></li>
  </ul>
  
  <p>But no commit message and no commit date. Is there any way to get it from the fileset?</p>