docker-setup.sh

#!/bin/bash
# More seemless integration between git-bash/WSL/Cygwin and Docker for Windows

set -euo pipefail
( [ -d 'C:\'] && cygpath . > /dev/null; ) || \
    { echo 'Must be run from GitBash, Msys or Cygwin'; exit 1; }

export MSYS_NO_PATHCONV=1
USER="$(whoami)"
docker run \
  -v /host_mnt:/host_mnt -v /:/host \
  --rm alpine \
  sh "
    mkdir -p /host/cygdrive /host/mnt /home
    # MSys/Msys2/GitBash
    ln -fs /host_mnt/c /host/c
    ln -fs /host_mnt/c /host/C
    # WSL
    ln -fs /host_mnt/c /host/mnt/c
    # Cygwin
    ln -fs /host_mnt/c /host/cygdrive/c
    ln -fs /host_mnt/c /host/cygdrive/C
    if [ $HOME = /home/$USER ]; then
        ln -fs $(cygpath -w "$HOME" | sed 's|^[cC]:|/host_mnt/c|; s|\\|/|g;') /host/home/$USER
    fi
    true"

I no longer like approach and I plan to delete. It's here for reference until thin.