You could try cding to the snacks.nvim directory in the error message, and running the suggested git restore command.
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So, I ran the git status and it came up with 282 files to delete:

Then I run the git restore and it says nothing:

And when I restart Neovim, it starts cloning the repo again, and ends right back at the same error "Clone succeeded, but checkout failed".
Oh sorry, I see you did run the exact command. Maybe delete that directory?
I've done it clean (without the directory) and get the same result.
Interestingly, in chatting with someone else, they referenced a stackoverflow post that mentioned doing a git checkout HEAD, which I did and resulted in a clean repository. But, Lazy keeps trying to re-clone the repository and comes up with the same error everytime.
Are you maybe low on disk space?
Nope - 700G free.
What does git status say?
Sorry to start a new branch, but I tried something else... I tried installing Astro -- and it has the same issue: failing to get snacks.nvim installed.
Given that this is happening with two packages, I can't help but think there is something weird with the snacks repository. I am getting everything else cloned and installed without issue.
(And, before someone asks..... I 100% nuked: ~/.config/nvim, ~/.local/share/nvim, ~/.local/state/nvim, and ~/.cache/nvim -- so everything was clean when I tried the install.)
