Include files and also copy them to output - jekyll

Question

In a Jekyll powered page, I have a set of files located in:
_includes/stuff/
I put those files there so that I can include them in other Markdown pages using:
{% include stuff/example.txt %}
This works as expected.
However, I also want to copy those files to the generated page so that I can link to them and that people can follow those links to download them. But by definition, stuff stored in directories starting with an underscore are not copied by Jekyll.
Another approach also didn't work. I put the files in an own top folder called stuff. This copies the folder to the final site. However, I'm not able to include a file from this folder. It seems include_relative only allows including files below the current one. For example, the following don't work:
{% include_relative stuff/example.txt %}
{% include_relative /stuff/example.txt %}
{% include_relative ../stuff/example.txt %}
Any ideas how I can achieve including and copying at the same time?

Answer 1

This works from index.html
{% include_relative example.txt %} for example.txt
{% include_relative stuff/example.txt %} for stuff/example.txt
{% include_relative /stuff/example.txt %} for stuff/example.txt
stuff/example.txt
class Toto
def dototo
myvar = "toto"
end
end
index.html
{% assign codeurl = "stuff/example.txt" %}
{% highlight ruby %}
{% include_relative {{codeurl}} %}
{% endhighlight %}
link to code
if codeurl == "/stuff/example.txt" this generates a link relative to site root
this may need {{site.baseurl}} prepended if your site is not at the root
of a domain (eg: user.github.io/repository)
link to code
For security reasons, this will not work :
{% include_relative ../stuff/example.txt %}
Just to avoid directory traversal
{% include_relative ../../../../../../../../../../../../etc/pwd %}
If you want to put you files in _includes/stuff you will need to do an include: [ /_includes ] in _config.yml, that will include all files in _includes as static files. Not very clean as you cannot filter subdiretories like include: [ /_includes/stuff ] to import only your stuff files.
Note : a dirty trick allows you to import only _includes/stuff/*.txt but I think it's really dirty.
# _config.yml
include:
- "_includes"
- "stuff"
- "*.txt"
exclude:
- "_includes/*.*"