git merge two repos

git-merge-repos

Using submodules - it's good if repos are unrelated or developed separately
see http://www.kernel.org/pub/software/scm/git/docs/v1.5.6/git-submodule.html

Either copy repository A into a separate directory in larger project B, or (perhaps better) clone repository A into a subdirectory in project B. 
Then use git submodule to make this repository a submodule of a repository B.

Using subtree - real merge
see http://nuclearsquid.com/writings/subtree-merging-and-you/

```
cd into repo Aproject
mkdir dir-B
git remote add -f Bproject /path/to/B
git merge -s ours --allow-unrelated-histories --no-commit Bproject/master
git read-tree --prefix=dir-B/ -u Bproject/master
git commit -m "Merge B project as our subdirectory"
# this will trigger a rebase and you may need to fix conflicts
git pull -s subtree Bproject master
```

At this point dit-B was gone but the repos merged.
git log doesn't show commits for Bproject, but Bproject files have commit history.

# source https://stackoverflow.com/questions/1425892/how-do-you-merge-two-git-repositories/10548919#10548919