Documentation: Standalone Installation Note

[skyethepinkcat]

Added a note to the standalone installation instructions, which recommends adding -I ~/.nix-defexpr/channels to the nix-shell command if home-manager cannot be found.

Description

This is just a documentation update -- I've previously run into issues where after adding the home-manager channel as a user, it would not show up in the $NIX_PATH, I thought it'd be a good idea to mention it.

[stale[bot]]

Thank you for your contribution! I marked this pull request as stale due to inactivity. Please read the relevant sections below before commenting.

If you are the original author of the PR

• GitHub sometimes doesn't notify people who commented / reviewed a PR previously when you (force) push commits. If you have addressed the reviews you can officially ask for a review from those who commented to you or anyone else.
• If it is unfinished but you plan to finish it, please mark it as a draft.
• If you don't expect to work on it any time soon, please consider closing it with a short comment encouraging someone else to pick up your work.
• To get things rolling again, rebase the PR against the target branch and address valid comments.

If you are not the original author of the PR

• If you want to pick up the work on this PR, please create a new PR and indicate that it supercedes and closes this PR.

[Zocker1999NET]

I assume your solution does (attempt to) fix #3091. In that context: is your proposal a long-term solution? Because, while I also tried to fix #3091 for myself, I discovered this issue has something to do with https://github.com/NixOS/nix/issues/2033#issuecomment-1366974053. So I tried:

• Using a different command for nix-env at the installation. This worked for the first generation but afterwards I still was not able to execute any home-manager command because it did not found the channel again.
• Attempted to change NIX_PATH persistently (e.g. https://github.com/NixOS/nix/issues/2033#issuecomment-744059453). This worked persistently, but I wasn’t quite happy with that.

In the end, I decided to add those channels using sudo to have all nix-channels I use together. And it also fixes #3091 persistently for me.