Add nested vcs dependency subdirectory when locking to Pipfile.lock (Fix #6120)

[AlexandreArpin]

The issue

When installing a package that has a vcs dependency with a subdirectory, the subdirectory isn't added to the Pipfile.lock.

This is a tentative fix for #6120

The fix

When formatting the vcs requirement for lockfile in format_requirement_for_lockfile

• normalize_vcs_url to clean the vcs's url as is done in install_req_from_pipfile - this removes the fragments from the url
• Inspect and add the req.link.subdirectory_fragment to the lockfile if parsed by the Link object

As discussed in #6120, alternatives could have been to honor #4259 and work on the install portion to be able to resolve correctly the Pipfile entry with the subdirectory as a vcs url fragment.

The checklist

• Associated issue
• A news fragment in the news/ directory to describe this fix with the extension .bugfix.rst, .feature.rst, .behavior.rst, .doc.rst. .vendor.rst. or .trivial.rst (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.

[AlexandreArpin]

From: #6120 (comment)

@AlexandreArpin your patch sounds like the right direction to head in -- I'm getting lock resolution errors though with the egg fragment syntax, does your patch resolve for that as well?

There was some discussion in #6095 about how the egg fragment syntax was deprecated?

I opted not to parse it and add it in the patch with that context.

I'd be happy to look into fixing the issue you mentioned in your comment if you'd like :)

[oz123]

Looks good.