GIT MERGE a repo with a folder in another repo without loosing history

Question

I have two repositories, let's say Repo A and Repo B with the structures as shown below:

Repo A (there are many files in each repo. I am just showing 2 files for example):
  |
  |
  |---Test1.cs  (It has some changes made by X Developer)
  |---Test2.cs  (It has some changes made by X Developer)

Repo B:
  |
  |
  |---src
       |
       |
       |---Test1.cs  (It has some changes made by Y Developer)
       |---Test2.cs  (It has some changes made by Y Developer)

I want to merge (or rebase) of files from Repo A to Repo B/src without loosing history. After the merge, when I view history, I want to see both Developer X and Y changes. Is this possible? If yes, please guide me how to do this.

I have looked other SO posts and tried adding remote repo...etc. But those are not covering this type of scenario. My GIT version is 2.21.0.

Answer 1

You can use a normal merge for this, but you will have to use merge --allow-unrelated-histories to allow unrelated histories to merge.

For example:

cd target-repository
# we work on master
git checkout master
# add the repository as a remote
git remote add other /path/to/source-repo
# fetch the remote repository, which will create other/master
git fetch other
# merge the histories, specifiy --allow-unrelated-histories to avoid the related history check
git merge --allow-unrelated-histories other/master

This assumes that files do not overlap.