Avoid recursing when installing a project to a subproject via copytree

[djbelknap]

resolves #9719

Problem

When installing a local package that contains the current project as a subfolder (like the integration_tests project in dbt-utils), if the symlink fails the copytree recursively copies the current project repeatedly until the path length limit is reached.

Solution

Use the ignore parameter of copytree to ignore the current project's packages directory to avoid repeated recursion.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR (Let me know if you'd like a test specific to this fix)
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX
• This PR includes type annotations for new and modified functions

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[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.84%. Comparing base (33161a3) to head (e10b698).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9734      +/-   ##
==========================================
+ Coverage   88.82%   88.84%   +0.01%     
==========================================
  Files         180      180              
  Lines       22584    22584              
==========================================
+ Hits        20060    20064       +4     
+ Misses       2524     2520       -4     

Flag	Coverage Δ
integration	86.13% <0.00%> (+<0.01%)	⬆️
unit	62.15% <100.00%> (ø)

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

Components	Coverage Δ
Unit Tests	62.15% <100.00%> (ø)
Integration Tests	86.13% <0.00%> (+<0.01%)	⬆️

[dbeatty10]

What

"Don't install yourself into your own dbt_packages folder."

How

shutil.copytree recursively copies an entire directory tree rooted at src to a directory named dst.

The new ignore parameter introduces a base case under which this recursion should stop. It essentially says:

"No dbt project ever needs to install itself within its own packages_install_path folder 😄. So when the current directory being processed is the same as this dbt project, then do not recursively copy the configured packages_install_path directory because it's already covered. Just ignore it!"

Why

The ignore parameter is being added here to prevent a dbt project from installing itself via dbt deps. As mentioned in #9719, this can happen if:

1. a dbt project is a subfolder of a local dependency listed within packages.yml, and
2. the host operating system doesn't support symlinks.

The 1st item is common for CI testing for packages like dbt_utils, and the 2nd is most common in legacy versions of Windows.

[dbeatty10]

Windows 10 users can possibly avoid this code path by turning on Developer Mode (which may allow creating Symbolic Links without requiring admin privileges) [1].

But this PR is specifically intended to cover the case where the user's system doesn't allow symlinks for whatever reason. So Developer Mode for Windows 10 is not a sufficient workaround for all cases.