[Windows + MSYS2/fish + NeoVIM] error: Error reading script file '/s' when running `PlugUpdate`

Run `nvim -c PlugUpdate` and got this:


Please give some hints on where to look further about this issue.

------------------------------

```
" vim-plug
call plug#begin('~/.vim/plugins')
Plug 'tpope/vim-sensible' " settings that make sense
Plug 'joshdick/onedark.vim' " color theme
Plug 'airblade/vim-gitgutter' " reflect git changes per line
Plug 'sheerun/vim-polyglot' " syntax highlighting for languages
Plug 'scrooloose/syntastic' " syntax checker for languages
Plug 'romgrk/barbar.nvim' " tabline
Plug 'vim-airline/vim-airline' " statusline
Plug 'vim-airline/vim-airline-themes' " status bar theme
Plug 'godlygeek/tabular' " text filtering and alignment
Plug 'chiel92/vim-autoformat' " code formatting
Plug 'kyazdani42/nvim-web-devicons' " icons

call plug#end()
```

```
NVIM v0.8.3
Build type: RelWithDebInfo
LuaJIT 2.1.0-beta3
Compiled by runneradmin@fv-az171-224

Features: -acl +iconv +tui
See ":help feature-compile"

system vimrc file: "$VIM\sysinit.vim"
fall-back for $VIM: "C:/Program Files (x86)/nvim/share/nvim"

Run :checkhealth for more info
```

- Type:
- [?] Bug
- [ ] Enhancement
- [ ] Feature Request
- [x] Question
- OS:
- [ ] All/Other
- [ ] Linux
- [ ] macOS
- [x] Windows
- Vim:
- [ ] Terminal Vim
- [ ] GVim
- [x] Neovim
- Git:
- [x] MSYS2
- Shell:
- [x] fish

# Workaround

```shell
SHELL= nvim -c PlugUpdate
```