[thu]

Are you sure it is related to entering an existing container (and running a new process) ?

From reading the README file, it seemed to me it was only spawning a login shell process in a new container (not an existing one), and possibly resuming an existing container.

[StavrosK]

You are correct, dockersh is a shell. It spawns a "proper" shell (e.g. bash) in a docker container when you log in.