How to share files across folders or repositories

Question

I'm working on a code snippet which has to work across multiple themes.

Let's say I have three themes:

• Orange
• Green
• Blue

Every theme has a folder called "snippets" inside, and I put my code snippet there.

• Orange/snippets/code.html
• Green/snippets/code.html
• Blue/snippets/code.html

The "code.html" file is exactly the same across every theme. I keep track of it in its own GitHub repo and then copy and paste to every theme repo.

How can I edit this snippet in one place and be sure that it gets updated in all themes? I'm looking for a method that would be scalable, as soon the number of themes may grow till 20-30.

In my situation I have more files then an example with "code.html" - they are in two folders, and the total amount is around 10.

I was reading about Git submodules, but I don't feel confident like they fit my issue. I'm not sure if this issue is related to Git at all, sorry about that.

P.S. I'm working on SaaS - Shopify to be exact. So any kind of PHP tricks will not work in this case. I need files to be processed in some way locally.

Edit: Real life example:

I have those 4 files:

{{ theme }}/snippets/file1.liquid
{{ theme }}/snippets/file2.liquid
{{ theme }}/assets/file3.liquid
{{ theme }}/assets/file4.liquid

I cannot create sub-directories or other directories.

Answer 1

Let say you have your common code in a repository. You could create a submodule in <Theme>/snippets/common. And keep it updated to the latest master every time you want to build/deploy your theme.

That means your code.html will be in <Theme>/snippets/common/code.html

cd <Theme>/snippets

# To add the submodule 
git submodule add <common code repository> common
# 2 new files will be added to the repository
# .gitmodules and the "common" folder

# When you clone the repo in another machine
# Always do the following command 
# to get the files from the common repository
git submodule update --init

# If you made a change in the common repository
git submodule update --remote