git subtree push changes back to subtree project
For the behavior you want, I think you'll have to push from Master, I don't know of a way to pull subtree changes from Slave.
To push changes:
(in Master)$ git subtree split --prefix=lib/slave -b split-branch$ git push <bare Slave repo> split-branch:master$ git branch -d split-branch$ cd /path/to/Slave/working/copy$ git pull # (now in Slave)The first command creates a new subtree based on the directory, which is then pushed to the other project.
In theory, you should be able to push directly to a working copy, but in practice that didn't work for me.