Log / error when git missing when running pip-tools

[jeffwidman]

See discussion here: #6609 (comment)

What happens if git isn't present?
If an error in creating a git repo results in pip-tools updates completely breaking, then it'd be nice to at least have an info log for easier debugging... don't have to capture the full subprocess, but instead we could log saying "couldn't create git repo, all pip-tools jobs will fail"...

And we probably should just outright bail here, no point in continuing the job if we know pip-tools will fail.

This was added in 4e72d4e which thankfully included a spec for the behavior.

Currently exists two places:

dependabot-core/python/lib/dependabot/python/update_checker/pipenv_version_resolver.rb

Lines 316 to 321 in f11c364

	# Initialize a git repo to appease pip-tools
	begin
	run_command("git init") if setup_files.any?
	rescue Dependabot::SharedHelpers::HelperSubprocessFailed
	nil
	end

and

dependabot-core/python/lib/dependabot/python/file_updater/pipfile_file_updater.rb

Lines 201 to 203 in f11c364

	# Initialize a git repo to appease pip-tools
	command = SharedHelpers.escape_command("git init")
	IO.popen(command, err: %i(child out)) if setup_files.any?

The second usage is surprising because it's in file_updater/pipfile_file_updater.rb, whereas pip-tools is actually pip-compile so I'd expect it to use file_updater/pip_compile_file_updater.rb instead. So possibly we don't need git there at all`, or possibly we do need it, but the code comment is wrong.

For the first one, we should also check if this is even still needed, as it may not be.

[jeffwidman]

The root need for this might have been removed as part of:

• Use download_dir=None for editable PyPI dependencies jazzband/pip-tools#385

I'll try it and see. 😁

[jeffwidman]

Looks like removal breaks CI over in:

• Experiment: Try disabling git init to see if pip-tools still breaks #6619

After looking deeper at the CI failure, it looks like the lack of git only causes breakage in a handful of situations. So we shouldn't raise, just need to add an info log.

This isn't a super high risk issue and it's very approachable for someone new to the project, so I'm going to tag it as a "good first issue" and leave it for a potential contributor. You can use this PR as an example of how to add a new log line:

• Log when go mod tidy fails #6601

[jeffwidman]

I ran across this again in the source code, so this time reached out to the pip-tools maintainers:

• Work with pip-tools maintainers to drop special requirements of git init before installing python #7612
• Remove the requirement that pip-tools must be run within a git repo jazzband/pip-tools#1931

I also re-opened:

• Experiment: Try disabling git init to see if pip-tools still breaks #6619

[GarryHurleyJr]

Please leave this one for new joining person as it should be simple