fix: allow variable expansion

[fecet]

Fix: Allow Variable Expansion in Bash Activation Scripts

Summary

This PR fixes an issue where environment variable values containing references like ${CONDA_PREFIX} were not being expanded correctly in bash activation scripts per prefix-dev/pixi#4122

Problem

In #1392, environment variable values with $ symbols were quoted using single quotes. While this quoting ensures correctness for many shell values, it prevents variable expansion in bash:

export PATH='${CONDA_PREFIX}/bin:$PATH'  # Variables not expanded

This breaks expected behavior for users relying on dynamic paths such as ${CONDA_PREFIX}/bin.

Fix

Values containing variable references are now quoted using double quotes instead of single quotes in bash activation scripts. This preserves correct expansion while still protecting the value from word splitting or globbing.

export PATH="${CONDA_PREFIX}/bin:$PATH"  # Variables are expanded

Impact

• Restores compatibility with tools relying on environment variable expansion (e.g., pixi)
• Affects only bash quoting behavior; other shells remain unchanged

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Let me know if you'd like to include a test case or changelog entry as well.

[lucascolley]

Ahh, I wonder whether this explains something I was seeing with nushell and zsh also?? scipy/scipy#23361 (comment)

[fecet]

You can try my fork to test this https://github.com/fecet/pixi/releases/download/v0.50.0/pixi-x86_64-unknown-linux-musl

[Hofer-Julian]

Thanks for the fix, I tried to think of a more general approach, but it's just a bit of a messy situation and your solution is a good one :)

Pushed a commit to make the shlex error case a bit nicer