feat(python): Auto-activate venv when cd'ing into directory

plugins/python/python.plugin.zsh

@@ -81,3 +81,18 @@ function mkv() {
   echo >&2 "Created venv in '${venvpath}'"
   vrun "${name}"
 }
+
+# Virtual environment is assumed to be named "venv".
+# Set VENV_NAME to another name if you use a different name, maybe ".venv".
+# To disable, set DISABLE_AUTO_VRUN to anything. Unset to re-enable.
+auto_vrun() {
+    [ $DISABLE_AUTO_VRUN ] && return 0
+    local venvpath=${VENV_NAME:-'venv'}
+    if [ -e "${venvpath}/bin/activate" ]; then
+        source "${venvpath}/bin/activate" > /dev/null 2>&1
+    else
+        [ -n "$(command -v deactivate)" ] && deactivate > /dev/null 2>&1
+    fi
+}
+add-zsh-hook chpwd auto_vrun
+auto_vrun