Add copy config option

Add an option to copy file instead of symlink, e.g.

- link:
    ~/.zshrc:
      copy: true
      path: zshrc

[anishathalye]

Would it be better to just have a separate copy: thing like link: ?

[eengstrom]

@jmigual - I offer an alternative for your use case that I use:

First, I define an environment variable, ${DBOT_TARGET_DISTRO}, which is set in mydotbot wrapper script. Then, with a file ~/.gitconfig-windows or ~/.gitconfig-linux or whatever, you can link the distro-local file like this:

- link:
    # add some distro-specific symlinks
    ~/.gitconfig-local:
      path: ~/.gitconfig-${DBOT_TARGET_DISTRO}
      if: '[ -n "$DBOT_TARGET_DISTRO" ]'

Finally, include that in your main~/.gitconfig file like this:

[include]
  path = ~/.gitconfig-local