autoenv_init: Only activate envs between PWD and previous dir

[tomtseng]

Fixes #228.

Issue

Suppose we cd from /a/b/c to /a/y/z.

Expected behavior: Presumably we've already invoked /.env, /a/.env, and /a/b/.env when we cded into /a/b/c, so I expect now cding into a/y/z/ to only invoke /a/y/.env and /a/y/z/.env.

Actual behavior: Invokes envs in all ancestors of /a/y/z: /.env, /a/.env, /a/y/.env, and /a/y/z/.env.

Changes

• In autoenv_init(), when traversing up from /a/y/z, stop traversing once the previous directory /a/b/c is a child of the currently travsed directory.

[hyperupcall]

Thanks for the PR! Although this is a clean fix, I worry that addressing this issue will cause breakage. The readme states:

When executing, autoenv, will walk up the directories until the mount point and execute all .env files beginning at the top.

I don't want to make any changes that run contrary to that, since it's the intended behavior, even if it's possibly counter-intuitive.

I thought of one tangible case that could break downstream consumers:

• An .env file at /home/user/.env with contents export GITHUB_TOKEN=... (assume token has "general permissions")
• An .env file at /home/user/Projects/project1/.env with contents export GITHUB_TOKEN=... (assume token has "specific permissions")
• When cding from /home/user/Projects/project1 from /home/user/Projects/project2, these new changes will no longer source /home/user/.env, meaning the token with the "general permissions" will not be used.