situation.
In this example, let's say you have the repository at `/path/to/B` (but
-it can be an URL as well, if you want). You want to merge the 'master'
+it can be a URL as well, if you want). You want to merge the 'master'
branch of that repository to the `dir-B` subdirectory in your current
branch.
----------------
$ git remote add -f Bproject /path/to/B <1>
-$ git merge -s ours --no-commit Bproject/master <2>
+$ git merge -s ours --no-commit --allow-unrelated-histories Bproject/master <2>
$ git read-tree --prefix=dir-B/ -u Bproject/master <3>
$ git commit -m "Merge B project as our subdirectory" <4>