Repo1 to merge into repo2, for example, in general, there are four steps:
In repo2 clone to a local directory code:
1. git remote add repo1 <repo1 address>
2. git fetch repo1
3. git branch repo1 repo1 / master (still master branch) or git checkout -b repo1 repo1 / master (will enter into repo1branch)
4. Perform the master branch: git merge repo1
Reference article
https://www.cnblogs.com/drizzlewithwind/p/8951910.html
https://www.jianshu.com/p/da2ba8bb0448