Empty Git log with certain future dates

[TTitcombe]

Describe the bug
The "Unreleased" section gets git commits in a date range between the last version tag and some future date. The future date used to be 2100-12-31, but this began to yield empty commits for some reason. To circumvent this issue, #17 changed the date to 2099-01-01, which seems to work. On limited testing, only some future dates in 2100-01-DD work.

To Reproduce
Steps to reproduce the behavior:

1. Run git log --since 2021-12-30 --until 2100-12-31 This should not yield anything
2. Run git log --since 2021-12-30 --until 2099-01-01. This should yield commits

Expected behavior
All the commits since the --since date should be returned.
Perhaps the Unreleased section should be updated so it only calls git log with a --since tag but no --until tag. Either that or discover what the issue with git log dates is.

Screenshots
N/A

System:

• OS: ubuntu 20.04
• Python version: 3.8
• Doculog version: 0.1.4

Additional context
N/A