How to combine two separate unrelated Git repositories into one with single history timeline

Question

I have two unrelated (not sharing any ancestor check in) Git repositories, one is a super repository which consists a number of smaller projects (Lets call it repository A).

Answer 1

I did something similar (merge history from B into A) like this:

1. go to your repo A
2. git fetch master:new-branch-on-A (so, you have copied master branch of B into a new branch 'new-branch-on-A' into your repo A.
3. git checkout new-branch-on-A
4. git rebase master (you rebase the new-branch-on-A with the master branch)
5. resolve conflicts if there are any
6. git checkout master
7. git merge new-branch-on-A
8. git branch -d new-branch-on-A
9. Done :), your histories are merged. I think all commits from A are before commit from B in the new history (git rebase -i is your friend if needed).