nix-prefetch-git symlink error on macos

[jdelStrother]

Describe the bug

nix-prefetch-git doesn't seem to work for me on macos with the 24.11-beta tag - it complains that /tmp is a symlink (which it is, it links to /private/tmp).

Steps To Reproduce

$ nix run github:nixos/nixpkgs/24.11-beta#nix-prefetch-git -- --url https://github.com/IFTTT/polo.git --rev 316aa2ac210a45a7fc400ab921831493d5dd21b8 --hash sha256
Initialized empty Git repository in /private/tmp/git-checkout-tmp-MzN6ZcNg/polo-316aa2a/.git/
remote: Enumerating objects: 51, done.
remote: Counting objects: 100% (51/51), done.
remote: Compressing objects: 100% (42/42), done.
remote: Total 51 (delta 8), reused 19 (delta 5), pack-reused 0 (from 0)
Unpacking objects: 100% (51/51), 19.57 KiB | 668.00 KiB/s, done.
From https://github.com/IFTTT/polo
 * branch            HEAD       -> FETCH_HEAD
Switched to a new branch 'fetchgit'
removing `.git'...
error: path '/tmp' is a symlink

Expected behavior

Successfully fetches a git repo into the store

Additional context

The same command works fine with 24.05:

$ nix run github:nixos/nixpkgs/24.05#nix-prefetch-git -- --url https://github.com/IFTTT/polo.git --rev 316aa2ac210a45a7fc400ab921831493d5dd21b8 --hash sha256
Initialized empty Git repository in /private/tmp/git-checkout-tmp-22f9iAdj/polo-316aa2a/.git/
remote: Enumerating objects: 51, done.
remote: Counting objects: 100% (51/51), done.
remote: Compressing objects: 100% (42/42), done.
remote: Total 51 (delta 8), reused 19 (delta 5), pack-reused 0 (from 0)
Unpacking objects: 100% (51/51), 19.57 KiB | 715.00 KiB/s, done.
From https://github.com/IFTTT/polo
 * branch            HEAD       -> FETCH_HEAD
Switched to a new branch 'fetchgit'
removing `.git'...

git revision is 316aa2ac210a45a7fc400ab921831493d5dd21b8
path is /nix/store/nljjjs2idzm9j5iy9swppd37z6aq96fb-polo-316aa2a
git human-readable version is -- none --
Commit date is 2022-04-04 16:29:34 -0700
hash is 1vikzclg64lpydfwvz2imzwvl2f2vv1iq9ww43ah31p84w2xfmih
{
  "url": "https://github.com/IFTTT/polo.git",
  "rev": "316aa2ac210a45a7fc400ab921831493d5dd21b8",
  "date": "2022-04-04T16:29:34-07:00",
  "path": "/nix/store/nljjjs2idzm9j5iy9swppd37z6aq96fb-polo-316aa2a",
  "sha256": "1vikzclg64lpydfwvz2imzwvl2f2vv1iq9ww43ah31p84w2xfmih",
  "hash": "sha256-MFbXBSfohgHVIJwnHMPewgm6+a9R/M1d85cS8yj7M+4=",
  "fetchLFS": false,
  "fetchSubmodules": false,
  "deepClone": false,
  "leaveDotGit": false
}

I'd originally posted this in nixpkgs, but then bisected it down to 9a94e07, so I'm guessing the problem is actually in nix itself..?

Metadata

nix-env (Nix) 2.18.8

(though I believe that nix-prefetch-git is using 2.24, at least in the 22.11 release

Checklist

• checked [latest Nix manual] ([source])
• checked [open bug issues and pull requests] for possible duplicates

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