fix: Solve bug when changing permissions with no modification right

[pkrog]

Description

When trying to set execution mode for a file or setting permissions to cache directory, an error may occur if we have no modification right on the parent folder.
This error occurs regardless of the current permissions on the targeted file or folder.
Thus, even if we already have the required permissions on the targeted file or folder, the error occurs.

This pull request introduces a function has_permissions() that tests if we already have the wanted permissions on a file or folder.
This new function is used at the two places described above, in order to avoid a useless setting of permissions that would lead to an error.

Type of Change

• Bugfix
• Feature / enhancement
• CI / Documentation
• Maintenance

Checklist

• My code follows the general style and conventions of the codebase, ensuring consistency
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have run pre-commit run --all locally in the source folder and confirmed that there are no linter errors.
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes

[codecov]

Codecov Report

❌ Patch coverage is 89.47368% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.23%. Comparing base (4d706ef) to head (ca648c8).
⚠️ Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
libmamba/src/core/subdir_index.cpp	84.61%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4107      +/-   ##
==========================================
+ Coverage   51.21%   51.23%   +0.02%     
==========================================
  Files         239      239              
  Lines       28669    28677       +8     
  Branches     3008     3012       +4     
==========================================
+ Hits        14684    14694      +10     
+ Misses      13982    13980       -2     
  Partials        3        3              

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[pkrog]

Codecov Report

❌ Patch coverage is 97.14286% with 2 lines in your changes missing coverage. Please review. ✅ Project coverage is 63.63%. Comparing base (c641811) to head (ad237ab).
Files with missing lines Patch % Lines
libmamba/src/core/subdir_index.cpp 84.61% 2 Missing ⚠️
Additional details and impacted files

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Note that I am not responsible for the two lines in question. They were here before, thus already not tested.

[Klaim]

LGTM in essence but I would need a bit more documentation of the function.

As for the CI error on Windows, I'm not totally sure but I suspect the specific check is about a kind of permission not supported by that OS? Not sure.