I personally intensely dislike tools that change the environment based on the directory contents. I use an `exec` script in the root (or parent, sometimes) that just does this:

    ```
    #!/bin/bash

    source .venv/bin/activate
    exec $SHELL $@
    ```

That gives me a subshell with the virtual env active, and the path to the virtual env goes into $PS1 so I've got a very visible "you are working in this project" signifier.

I don't know why subshells aren't more popular for this sort of thing, they remove a lot of ambiguity (and subsequent opportunities to screw things up) for me.