title: Git: get blob path in .git directory
body: <p>I want to access some blobs at some point in repo history.</p>
  
  <p>Currently, I do that with <code>git show $REV:$PATH</code>. But files are quite large and I don't want them to be read and piped in script. I want to get their path and then read as plain files.</p>
  
  <p>May I rely on layout described in current documentation (e.g. <code>.git/objects/ee/2403ffd236587a2b17ddc35b0e711fc99ba6a0</code>), get file hash and transform it into path manually? I mean that it will not change soon in future versions and objects directory always has this structure.
  Is there simpler way to do that with some plumbing command?</p>