Tartufo pre-commit command does not scan files committed via git commit -am command

[jwinders-godaddy]

🐛 Bug Report

To Reproduce

Using tartufo 3.2.1 or 3.3.1

Following steps assume a local .pre-commit-config.yaml file with the following content:

repos:
- repo: https://github.com/godaddy/tartufo
  rev: v3.3.1
  hooks:
  - id: tartufo

mkdir tartufo-pre-commit-test
cd tartufo-pre-commit-test/
git init
touch test_file
git status
git add .
git commit
pre-commit install
cat test_file # file is empty
openssl rand -base64 40 > test_file # add some content that tartufo would flag
git commit -am "test" # this should result in tartufo complaining about the content, but with issue shows passing scan

Expected Behavior

Tartufo:pre-commit should scan files not explicitly staged via git add, but added via git commit -am
report issue.

Perhaps additionally, the command should indicate when there are no files being operated on by the command.

Environment

[mgaspar-godaddy]

I'll add to this that I tested back to version 3.1.3 and found that the pre-commit check would fail and present tartufo output indicating the offending content. However, as of version 3.1.4 the same test results in the pre-commit check passing.

Looking at v3.1.3...v3.1.4 it looks like #351 introduced a cached=True option into the code.

Pulling down the latest 3.3.1 version and taking out line 962

tartufo/tartufo/scanner.py

Line 962 in 81115e0

cached=True,

and testing in my dev environment with poetry I found removing the cached=True line results in the pre-commit check failing as expected.