Fix conan cache restore when restoring the same cache multiple times

[obnyis]

Changelog: Bugfix: Make conan cache restore work correctly when restoring over a package already in the local cache.
Docs: Omit

Close #15949

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[memsharded]

Thanks very much for your contribution, and thanks very much for the detailed report in the issue @obnyis

I see some tests are failing in Windows conans/test/integration/command_v2/test_cache_save_restore.py::test_cache_save_downloaded_restore, though I think our CI logs are closed at the moment (some security issues), it reports issues with the Windows paths:

The system cannot find the file specified: 'C:\\J\\t_v2\\4c3f\\PY36\\tmpykqzx4v6conans\\path with spaces\\.conan2\\p/pkgff8e5eaab3983/p' -> 'C:\\J\\t_v2\\4c3f\\PY36\\tmpykqzx4v6conans\\path with spaces\\.conan2\\p\\pkgff8e5eaab3983\\p'

This is something I can have a look if not easy to test in Windows for you

[memsharded]

Not very evident what this comparison is trying to protect against or do. I would say that these could match, and still the package should be restored, but it seems in some cases it would be skipped.

[memsharded]

Now I have understood it is an optimization to not have to process folders already in place

[memsharded]

I have pushed some minor changes mostly .replace("\\", "/") to make things work in Windows

[obnyis]

Thanks very much for your contribution, and thanks very much for the detailed report in the issue @obnyis

I see some tests are failing in Windows conans/test/integration/command_v2/test_cache_save_restore.py::test_cache_save_downloaded_restore, though I think our CI logs are closed at the moment (some security issues), it reports issues with the Windows paths:

The system cannot find the file specified: 'C:\\J\\t_v2\\4c3f\\PY36\\tmpykqzx4v6conans\\path with spaces\\.conan2\\p/pkgff8e5eaab3983/p' -> 'C:\\J\\t_v2\\4c3f\\PY36\\tmpykqzx4v6conans\\path with spaces\\.conan2\\p\\pkgff8e5eaab3983\\p'

This is something I can have a look if not easy to test in Windows for you

Ah sorry about that. I added a guard clause around the directory deletion just before I left for the night, and forgot to consider the implications on windows paths.

I'm fine with running windows tests :) just forgot to set up a copy before I pushed this up

[memsharded]

Thanks very much for contributing this. It is merged, it will be in next 2.3 release.