Is there a way to handle multiple projects with lots of duplications?

Question

I have two projects.

First I wrote the project number 1.
Then I decided to start project number 2 which was very similar to project number 1.
So I decided to clone the project number 1 and start from there.

The challenge is developing these two projects.

From now on, some changes in project number 1 have to be done in project number 2.
My problem is that I have to copy and paste some of new changes in project 2 which is exhausting and may cause problems (such as forgetting copying and pasting some codes).

Did you have any experience about this issue?
Or do you have any solutions?

Answer 1

If you have common parts limited to a folder (and subfolders), you can:

• extract that folder in its own repository
• reference that third repository as submodule (following its main branch)

That way, each time you are making a change to that common parts in repo1, all you need to do in repo2 to get updated is:

cd repo2
git submodule update --remote