git.get_commits error check

[bhelgs]

Description

git.get_commits could potentially fail silently.

The first commit is the fix. See the git commit message for more info on all following commits (broken up for easier review).

The final commit also improves error checking in git.get_tags (closes #518).

Checklist

• [x] Add test cases to all the changes you introduce
• [x] Run ./scripts/format and ./scripts/test locally to ensure this change passes linter check and test
• [x] Test the changes on the local machine manually
• [x] Update the documentation for the changes

Expected behavior

Fail fast behavior and better reports to the user when something goes wrong with git.

Some of the tests showed the command was failing for unexpected reasons (e.g. invalid commit range git log None..None).

Example of a silent failure that is now caught:

Without this change users with really old versions of git will see is "No commits found" but after the change: GitCommandError: fatal: unrecognized argument: --author-date-order

• reason: commands/changelog.py calls git.get_commits with --author-date-order but this argument is not valid for older versions of it.

Steps to Test This Pull Request

1. ran tests locally and formatted.

Additional context

[codecov[bot]]

Codecov Report

Merging #540 (7562808) into master (764861f) will increase coverage by 0.18%. The diff coverage is 98.75%.

@@            Coverage Diff             @@
##           master     #540      +/-   ##
==========================================
+ Coverage   98.25%   98.44%   +0.18%     
==========================================
  Files          39       39              
  Lines        1551     1603      +52     
==========================================
+ Hits         1524     1578      +54     
+ Misses         27       25       -2     

Flag	Coverage Δ
unittests	98.44% <98.75%> (+0.18%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
commitizen/git.py	99.27% <97.61%> (-0.73%)	:arrow_down:
commitizen/__version__.py	100.00% <100.00%> (ø)
commitizen/bump.py	100.00% <100.00%> (ø)
commitizen/changelog.py	100.00% <100.00%> (+0.56%)	:arrow_up:
commitizen/cmd.py	100.00% <100.00%> (ø)
commitizen/commands/changelog.py	98.85% <100.00%> (+2.25%)	:arrow_up:
commitizen/commands/commit.py	98.43% <100.00%> (+0.02%)	:arrow_up:
commitizen/commands/init.py	91.66% <100.00%> (ø)
commitizen/config/json_config.py	100.00% <100.00%> (ø)
commitizen/config/yaml_config.py	100.00% <100.00%> (ø)
... and 4 more

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[woile]

Thanks a lot!