Stop change CWD to .env/.flaskenv location

[greyli]

By the current implementation, if .env or .flaskenv was found in the top-level directory, Flask will change the current work directory to the directory that contains the .env or .flaskenv file.

When the user accidentally put a .env or .flaskenv in the top-level directory, then executing flask run in the current directory (contains app.py) will throw out NoAppException.

See more in #3561.

[davidism]

@jab any thoughts on this, especially in relation to #3108? I think your projects had setups that were affected by the cd.

[jab]

Thanks for the ping on this, @davidism. I can confirm these changes don't break anything in my customized Flask CLI (since mine does some more sophisticated detection of .env files that is independent of Flask's built-in detection, which I can explain more in #3108 or elsewhere).

And these changes seem good to me otherwise. Silently changing the CWD based on the presence/location of (hidden) .env files seems like it can break things in a hard-to-debug way for users. I may be missing something, since I'm not clear on what the benefit was in the first place. I'd expect users needing to compute paths relative to their app's modules should be doing so in a CWD-independent way (e.g. using __file__). If they're not, I guess this change could break them. But even if it does, it seems the benefits here outweigh that cost.

The only thing missing before I think this can be merged is an update to the changelog.

Thanks @greyli for contributing this!

[jab]

This looks good to me, and no one's raised any concerns, so I'm going to merge this before it stalls any longer.