how to use git merge -s subtree?

hi,

i recently noticed that the subtree merge strategy is missing from
merge-strategies.txt an i tried to first figure out how it works. i got
it to work, but i'm not 100% sure about i'm using it the way i'm
supposed to.

here is what i do:

1) git remote add B /path/to/B.git
2) git fetch
3) mkdir B
4) touch B/.gitignore
5) git add B/.gitignore
6) git commit -m "add empty B directory"
7) git merge -s subtree B/master

and yes, it works pretty well, but is this the right way? or is it
possible to somehow avoid steps 3..6?

thanks,
- VMiklos