title: git log for specific commit in branch
body: <p>I was searching a certain commit id in a specific branch, although the commit isn't in that specific branch I've got a result, while in git log there are no results.</p>
  <blockquote>
  <p>git log commit_id # finds commit</p>
  <p>git check a # branch 'a' doesn't contain commit_id</p>
  <p>git log # search for commit_id with no results.</p>
  </blockquote>
  <p>is that a bug or by design? if not a bug, then why?</p>
  <p>Thanks in advance.</p>