PATH updating seems a bit dodgy

[defhacks]

Describe the bug
relative or unqualified paths to mise alter $PATH unexpectedly

To Reproduce

Confirmed behaviour in both bash/zsh

relative paths yield an interesting result:

% ./mise activate zsh| grep PATH
export PATH=".:$PATH"
export __MISE_ORIG_PATH="$PATH"

but possibly more subtle and concerning is this case:

% mise activate zsh | grep PATH
export PATH=":$PATH"
export __MISE_ORIG_PATH="$PATH"

I was surprised to that both bash/zsh seem to interpret the empty string entry being pre-pended to $PATH here as adding the current working directory to $PATH.

I would propose patches to fix, but when I modified my local copy to prevent this behavior, I saw a comment about direnv, which I don't really use so I thought I'd just kick off the discussion rather than propose something that causes grief to direnv users.

[jdx]

do you have experimental enabled? that actually goes down a completely different code path (see #863 if you're curious what)

I'm not sure if that's related off the top of my head, but knowing that will help me know where to look.

I would very much appreciate some help with this particular part of the codebase btw. That code is a combination of a few things:

• it's old and since this is my first rust project, poorly written
• it's really hard to understand what it should be doing. It's heavily based on state.
• as a result of both, when I've made modifications I haven't taken a step back to refactor it very much, just adding bits of what I need

so it's a little bit of a train wreck—certainly the worst (but arguably most important) part of the codebase. I may have scared you off, but some fresh eyes might have some good ideas.