Doesn't work at the moment. It runs:

```bash
git --git-dir /Users/parker/code/parkermoore.de/.git log --format="%ct" /Users/parker/code/parkermoore.de/portfolio.html
```

... which returns nothing. When I change it to

```bash
git --git-dir /Users/parker/code/parkermoore.de/.git log --format="%ct" -- portfolio.html
```

it works. So it looks like it needs to be relative to the `top_level_git_directory`.