Add a mode to print git errors

[polac24]

Rehashed #56 without fork-PR

Introducing a mode that prints git output if a command fails.

• Pass --print_git_errors to enable that mode
• In the verbose mode is enabled, this argument is redundant (added a warning)

To test, invoke git-fastclone [email protected]:githubtraining/hellogitworld.git -b 1111 --print_git_errors which will try to check out to a non-existing 111.

git-fastclone 1.4.2
Cloning hellogitworld to ..../hellogitworld
I, [2023-06-27T12:41:07.545645 #90557]  INFO -- : error: pathspec '1111' did not match any file(s) known to git

[polac24]

CI to GH actions done in #58