title: Git error on checkout: "fatal: reference is not a tree"
body: <p>It all started when I decided to figure out why the project I'm working on weighs so much. I've run the following script:</p>
  <pre><code>git rev-list --objects --all \
  | git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' \
  | sed -n 's/^blob //p' \
  | sort --numeric-sort --key=2 \
  | cut -c 1-12,41- \
  | $(command -v gnumfmt || echo numfmt) --field=2 --to=iec-i --suffix=B --padding=7 --round=nearest
  </code></pre>
  <p>And figured out which commits have the heaviest files. Next, I would like to see who is the author of those commits and when trying to run something like:</p>
  <pre><code>git show --stat COMMIT_HASH
  </code></pre>
  <p>I get a pile of gobbledygook and when I try rolling back to the commit, I get the above mentioned error.</p>
  <p>So my question is: <strong>how do I find the author of the commit?</strong></p>