`which` isn't necessarily portable, but `command -v` is an equivalent form.

Additionally, the `\'` is not necessary, as it is already quoted by `"`.

This removes part of the PATH that were being added automatically in multi-user installs:

- $HOME/.nix-profile/lib/kde4/libexec - shouldn't be needed anymore, we are now using kde5
- @localstatedir@/nix/profiles/default/lib/kde4/libexec - same as above
- @localstatedir@/nix/profiles/default - shouldn't ever contain binaries

If the profile is sourced inside a script with `set -u`, the check for
__ETC_PROFILE_NIX_SOURCED and NIX_SSL_CERT_FILE would raise an error.
A simple guard around this check allows the script to operate under
standard environments (where it is fairly reasonable to assume USER
and HOME are set.)

Following the lead of the single user installer, if NIX_SSL_CERT_FILE is explicitly set prior to running, accept the user-provided version.

Note: don't backport to 2.0-maintenance

By passing --daemon or --no-daemon, the installer can be forced to
select one or the other installation options, despite what the
automatic detection can provide.

This commit can be backported to 2.0-maintenance because it explicitly
turns off the daemon installation for Linux under systemd.

We need nixpkgs to be set in NIX_PATH for Nix 1.12 to work correctly

We use grep instead of an equality check because it is difficult
to extract _just_ the user's note, instead it is prefixed with
some plist junk. This was causing the user note to always be set,
even if there was no reason for it.

Grep would ignore files that didn't exist, but would complain
about files in a directory if the directory didn't exist. Simply check
for the directory first, prior to grepping it.

 - darwin installer: delete hardware report, not necessary
 - moves os-specific code from the darwin installer to to `poly_*`
   functions
 - adds profile.d support to the profile targets, which automatically
   handles many distros which don't have a /etc/bashrc but do have an
   /etc/profile.d
 - /bin/bash -> /usr/bin/env bash
 - document why each excluded shellcheck check is excluded
 - rename the multi-user to Daemon-based

Checking for MANPATH without quotes always returns true, so that it breaks bash-completion for man pages on modern systems without MANPATH environment variable.

The default profile already loads /etc/bashrc.

This does not belong in Nix. Setting this env var is already done by the aspell derivation found in Nixpkgs.

The installer will error out if a user's shell configuration includes any mention of ~nix-profile~, even if this is in a comment. This change is designed to do the bare minimum to ignore lines beginning with a `#`.

In particular, drop the "build-" and "gc-" prefixes which are
pointless. So now you can say

  nix build --no-sandbox

instead of

  nix build --no-build-use-sandbox

Relevant RFC: NixOS/rfcs#4

$ ag -l | xargs sed -i -e "/\"/s/’/'/g;/\"/s/‘/'/g"

Also output in the status report that the user is very silly

Starve the TTY of input to ensure this works, but provide yes to the
current installer to handle the current broken case.

Don't install a second nix after the initial installation, and the rsync change fixes a bug hidden by the nix replacement where the store files were being owned by the installing user due to rsync's -a implying -og.

relevant directions

Prompt for sudo before validating assumptions, and check ourselves for root-owned files instead of making a scary warning.