Wrap up the project environment activate/deactivate methods in the cd command.

cd-with-auto-project-env.sh

# cd-with-auto-project-env.sh
#
# Wrap up the project environment activate/deactivate methods in the cd command.
#
# Custom
# ------
# 1. env : environment directory contained in the project root.
# 2. conda activate ./env : method to activate the target environment.
# 3. conda deactivate : method to deactivate the current environment.

# Prerequisite
# ------------
# The system variable $PYTHONPATH should have been set (or unset)
# when you're in (or out of) the project directory.
# Recommend to use the `direnv` tool for this purpose.

cd() {
    builtin cd "$1"
    if [ -n "$PYTHONPATH" ]; then
        conda activate "$PYTHONPATH"/env
        __conda_activated="True"
    elif [ -n "$__conda_activated" ] && [ -z "$PYTHONPATH" ]; then
        conda deactivate
        unset __conda_activated
    fi
}