Git modifies coverage issues based on remote repositories

problem description

There is now a Git repository A, which is constantly being updated. Then I cloned A, made some modifications to the code in repository A, and uploaded it to repository B. B has not been updated for a long time. Now I need to merge the latest A code into my B repository code, but it cannot overwrite the B repository code that I previously modified. Because I created a new branch in warehouse B, copied code A to the new branch of B, and then returned to the main branch of B to merge the new branch of B. However, this would cause the previously modified code of B to be overwritten by A. How do you do it?

The scenario where this problem arises: Based on the open-source repository A, some modifications have been made to form a new repository B. At the same time, repository A has undergone version updates, such as adding new features that need to be merged into repository B, but cannot overwrite the previous modifications made by B.

solution

You can merge the latest code from warehouse A into warehouse B by following these steps without overwriting the modifications you made in warehouse B. This process involves using Git's' rebase 'and' merge 'functions.

1. Add A as a new remote repository：

Firt ensure that you have added A as a new remote repository. You can do this by running the following command in the B repository.

cd path/to/B
git remote add upstream path/to/A

2. get the lastest code from A：

Get the latest code from A by running the following command in the B repository.

git fetch upstream

3. create a new branch to handle the merge：

create a new branch to handle the merge in the B repository.

git checkout -b merge-upstream

4. merge the latest code from A into your branch：

merge the latest code from A into your branch that you just created in the B repository.

git merge upstream/main

if A repository's main branch is not main, replace the branch name with the appropriate branch name.

if you get the error fatal: refusing to merge unrelated histories, you need to execute the following command

use --allow-unrelated-histories option to force Git to merge unrelated histories.

git merge upstream/main --allow-unrelated-histories

The 'fatal: referencing to merge unrelated histories' error occurs because Git considers the histories of the two repositories to be completely unrelated. To solve this problem, you can use the '-- allow unreleased histories' option to force Git to merge these unrelated history records.

5. fix conflicts：

If there are conflicts during the merge process, Git will prompt you. You need to manually resolve these conflicts, and then submit the solved code.

git add .
git commit

6. merge the merged branch into the main branch of repository B：

switch to the main branch of repository B and merge the merged branch into the main branch of repository B.

git checkout main
git merge merge-upstream

7. fix conflicts：

If there are conflicts during the merge process, Git will prompt you. You need to manually resolve these conflicts, and then submit the solved code.

8. push the merged code to the remote main branch of repository B：

Push the merged code to the remote main branch of repository B.

git push origin main

By following these steps, you can merge the latest code from A repository into B repository, without overwriting your modifications made in B repository. The key to this process is to create a new branch to handle the merge and merge the merged branch back into the main branch of B repository after solving conflicts.