* fix(pipenv): don't activate or leak errors when virtualenv is missing
* fix(pipenv): compare whole path components when deactivating
$PWD
$pipfile_dir is a string-prefix test, so moving from a project to an
unrelated sibling whose path merely starts with the same text (…/proj ->
…/proj-archive, …/projX) does not deactivate: the project's virtualenv
stays active in a directory that has no Pipfile. Require an exact match or
a component boundary instead. Subdirectories of the project keep their
current behaviour, and a project at / still matches everything.
Use add-zsh-hook to add functions to hooks. That way they won't be added again
when doing `source ~/.zshrc` multiple times.
Co-authored-by: Marc Cornellà <marc.cornella@live.com>