fix: Adapt root prefix' precedence for CONDA_ENVS_PATH

[holzman]

Fixes #3851.

$ mkdir -p /tmp/test/envs && CONDA_ENVS_PATH=/tmp/test/envs mamba create -n test1
Empty environment created at prefix: /tmp/test/envs/test1

[Hind-M]

We should also test having both of the environment variables set and check the precedence?

[holzman]

Sure, I wasn't sure the behavior was defined, but I'll check what mamba 1 and conda do when both are set.

[holzman]

Actually, setting both is not allowed in both conda and mamba 1, so the test is OK as written.

$ CONDA_ENVS_PATH=/tmp/envpath/envs CONDA_ENVS_DIRS=/tmp/envroot/envs mamba create --offline -n test1
Multiple aliased keys in file envvars:
  - envs_path
  - envs_dirs
Must declare only one. Prefer '_envs_dirs'

MultipleKeysError: Multiple aliased keys in file envvars:
  - envs_path
  - envs_dirs
Must declare only one. Prefer '_envs_dirs'

mamba 2 does allow both at the moment and CONDA_ENVS_PATH takes precedence.

I can create a separate PR to prohibit having both environment variables set.

[Hind-M]

Thank you for looking into it!
Hmm interesting, we should check indeed why these are not aliases in mamba 2 (but that would be in another PR).

[holzman]

Makes sense. I started looking into it and realized there's another incompatibility in the syntax.

In conda and mamba1, both CONDA_ENVS_DIRS and CONDA_ENVS_PATHS are path-separator delimited (colon on Linux, semicolon on Windows).

In mamba2, CONDA_ENVS_DIRS is comma-delimited instead.

[holzman]

Ok: submitted #3854 to address the case if someone sets both env vars and #3855 to unify the behavior using the path separator as delimiter.

[Hind-M]

Thanks!