Docker image doesn't contain git binary anymore

[bringabong]

Describe the bug
Since the last few releases (i think since 0.31.0), the official docker image doesn't contain the git binary anymore.

Because of this, the included script oxidized-report-git-commits.sh does not work anymore.

To Reproduce
Steps to reproduce the behavior:

1. Pull latest official docker image, and start the container
2. Log in to the container: docker exec -it oxidized /bin/bash

3. which git

4. [nothing]

Expected behavior
Find git binary in /usr/bin