Failure to install on julia nightly on Windows

[piever]

I've noticed during CI (see here) that this package does not install on Windows with julia nightly. The culprit seems to be Indexing.jl

Warning: failed to extract archive downloaded from https://pkg.julialang.org/package/313cdc1a-70c2-5d6a-ae34-0150d3930a38/0cf3ac621cd74b1d03af0cc4275f680b2070a5cc
└ @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:510
┌ Warning: failed to extract archive downloaded from https://api.github.com/repos/andyferris/Indexing.jl/tarball/0cf3ac621cd74b1d03af0cc4275f680b2070a5cc
└ @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:510
ERROR: GitError(Code:ERROR, Class:Checkout, cannot checkout to invalid path '\')
Stacktrace:
  [1] macro expansion
    @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\LibGit2\src\error.jl:110 [inlined]
  [2] checkout_tree(repo::LibGit2.GitRepo, obj::LibGit2.GitTree; options::LibGit2.CheckoutOptions)
    @ LibGit2 C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\LibGit2\src\repository.jl:358
  [3] checkout_tree_to_path(repo::LibGit2.GitRepo, tree::LibGit2.GitTree, path::String)
    @ Pkg.GitTools C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\GitTools.jl:82
  [4] install_git(io::Base.DevNull, uuid::Base.UUID, name::String, hash::Base.SHA1, urls::Set{String}, version::VersionNumber, version_path::String)
    @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:581
  [5] download_source(ctx::Pkg.Types.Context, pkgs::Vector{Pkg.Types.PackageSpec}, urls::Dict{Base.UUID, Set{String}}; readonly::Bool)
    @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:747
  [6] #download_source#39
    @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:646 [inlined]
  [7] download_source
    @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:644 [inlined]
  [8] up(ctx::Pkg.Types.Context, pkgs::Vector{Pkg.Types.PackageSpec}, level::Pkg.Types.UpgradeLevel)
    @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:1246
  [9] up(ctx::Pkg.Types.Context, pkgs::Vector{Pkg.Types.PackageSpec}; level::Pkg.Types.UpgradeLevel, mode::Pkg.Types.PackageMode, update_registry::Bool, kwargs::Base.Iterators.Pairs{Symbol, Base.DevNull, Tuple{Symbol}, NamedTuple{(:io,), Tuple{Base.DevNull}}})
    @ Pkg.API C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\API.jl:325
 [10] up(ctx::Pkg.Types.Context; kwargs::Base.Iterators.Pairs{Symbol, Any, NTuple{4, Symbol}, NamedTuple{(:level, :mode, :update_registry, :io), Tuple{Pkg.Types.UpgradeLevel, Pkg.Types.PackageMode, Bool, Base.DevNull}}})
    @ Pkg.API C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\API.jl:147
 [11] resolve(ctx::Pkg.Types.Context; kwargs::Base.Iterators.Pairs{Symbol, Base.DevNull, Tuple{Symbol}, NamedTuple{(:io,), Tuple{Base.DevNull}}})
    @ Pkg.API C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\API.jl:331
 [12] (::Pkg.Operations.var"#97#101"{String, Pkg.Operations.var"#107#109"{Bool, Cmd, Cmd, Nothing, Pkg.Types.Context, Vector{Tuple{String, Base.Process}}, String, Pkg.Types.PackageSpec}, Pkg.Types.PackageSpec})()
    @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:1445
 [13] with_temp_env(fn::Pkg.Operations.var"#97#101"{String, Pkg.Operations.var"#107#109"{Bool, Cmd, Cmd, Nothing, Pkg.Types.Context, Vector{Tuple{String, Base.Process}}, String, Pkg.Types.PackageSpec}, Pkg.Types.PackageSpec}, temp_env::String)
    @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:1369
 [14] (::Pkg.Operations.var"#96#100"{Pkg.Operations.var"#107#109"{Bool, Cmd, Cmd, Nothing, Pkg.Types.Context, Vector{Tuple{String, Base.Process}}, String, Pkg.Types.PackageSpec}, Pkg.Types.Context, Pkg.Types.PackageSpec, String, Pkg.Types.Project, String})(tmp::String)
    @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:1440
 [15] mktempdir(fn::Pkg.Operations.var"#96#100"{Pkg.Operations.var"#107#109"{Bool, Cmd, Cmd, Nothing, Pkg.Types.Context, Vector{Tuple{String, Base.Process}}, String, Pkg.Types.PackageSpec}, Pkg.Types.Context, Pkg.Types.PackageSpec, String, Pkg.Types.Project, String}, parent::String; prefix::String)
    @ Base.Filesystem .\file.jl:734
 [16] mktempdir(fn::Function, parent::String)
    @ Base.Filesystem .\file.jl:732
 [17] sandbox(fn::Function, ctx::Pkg.Types.Context, target::Pkg.Types.PackageSpec, target_path::String, sandbox_path::String, sandbox_project_override::Pkg.Types.Project)
    @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:1406
 [18] test(ctx::Pkg.Types.Context, pkgs::Vector{Pkg.Types.PackageSpec}; coverage::Bool, julia_args::Cmd, test_args::Cmd, test_fn::Nothing)
    @ Pkg.Operations C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:1581
 [19] test(ctx::Pkg.Types.Context, pkgs::Vector{Pkg.Types.PackageSpec}; coverage::Bool, test_fn::Nothing, julia_args::Cmd, test_args::Cmd, kwargs::Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
    @ Pkg.API C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\API.jl:406
 [20] test(pkgs::Vector{Pkg.Types.PackageSpec}; kwargs::Base.Iterators.Pairs{Symbol, Bool, Tuple{Symbol}, NamedTuple{(:coverage,), Tuple{Bool}}})
    @ Pkg.API C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\API.jl:143
 [21] test(; name::Nothing, uuid::Nothing, version::Nothing, url::Nothing, rev::Nothing, path::Nothing, mode::Pkg.Types.PackageMode, subdir::Nothing, kwargs::Base.Iterators.Pairs{Symbol, Bool, Tuple{Symbol}, NamedTuple{(:coverage,), Tuple{Bool}}})
    @ Pkg.API C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.7\Pkg\src\API.jl:159
 [22] top-level scope

(I don't have access to a Windows machine, so I can't really troubleshoot more than this, sorry!)