generated disko format hits shellcheck warnings, causing new luks-btrfs-raid-non-root test to fail

[SolidEva]

while testing #1098

❯ nix build --no-link ".#checks.x86_64-linux.luks-btrfs-raid-non-root"
warning: Git tree '/home/eva/repos/disko' is dirty
evaluation warning: mdadm: Neither MAILADDR nor PROGRAM has been set. This will cause the `mdmon` service to crash.
error: builder for '/nix/store/dwj0x1w3sphr78gav73kd0dnrj296anc-disko-format.drv' failed with exit code 1;
       last 25 log lines:
       >
       >
       > In /nix/store/4d9cm1sv51glxlfvbid2m1gqkhx862xp-disko-format line 355:
       >       IFS= read -r -s "$var"
       >                       ^----^ SC2229 (warning): This does not read 'var'. Remove $/${} for that, or use ${var?} to quiet.
       >
       >
       > In /nix/store/4d9cm1sv51glxlfvbid2m1gqkhx862xp-disko-format line 364:
       >         export password
       >                ^------^ SC2031 (info): password was modified in a subshell. That change might be lost.
       >
       >
       > In /nix/store/4d9cm1sv51glxlfvbid2m1gqkhx862xp-disko-format line 365:
       >         [ "$password" = "$password_check" ]
       >            ^-------^ SC2031 (info): password was modified in a subshell. That change might be lost.
       >
       >
       > In /nix/store/4d9cm1sv51glxlfvbid2m1gqkhx862xp-disko-format line 368:
       >         export password=disko
       >                ^------^ SC2031 (info): password was modified in a subshell. That change might be lost.
       >
       > For more information:
       >   https://www.shellcheck.net/wiki/SC2154 -- password_check is referenced but ...
       >   https://www.shellcheck.net/wiki/SC2229 -- This does not read 'var'. Remove ...
       >   https://www.shellcheck.net/wiki/SC2030 -- Modification of password is local...
       For full logs, run:
         nix log /nix/store/dwj0x1w3sphr78gav73kd0dnrj296anc-disko-format.drv
error: 1 dependencies of derivation '/nix/store/p28v5l27yyd24asb87fgfb449am2nmpn-nixos-test-driver-disko-luks-btrfs-raid-non-root.drv' failed to build
error: 1 dependencies of derivation '/nix/store/lydfhigmi2x9h18s0iyjy05jx8s9hi2p-vm-test-run-disko-luks-btrfs-raid-non-root.drv' failed to build

looking at the full log, we also hit the following warning:

In /nix/store/4d9cm1sv51glxlfvbid2m1gqkhx862xp-disko-format line 146:
        [ "$password" = "$password_check" ]
                         ^-------------^ SC2154 (warning): password_check is referenced but not assigned.

[GotFlojo]

Seems like I'm hitting a similar issue. Also btrfs related possibly?! I'm not using raid though just btrfs/luks.
I'm getting similar shellcheck errors about $var and also the same $password_check related error as @SolidEva.

I'm using

disko = {
      url = "github:nix-community/disko/latest";
      inputs.nixpkgs.follows = "nixpkgs";

where nixpkgs=nixos-25.05

error: builder for '/nix/store/nwkn8awvj95a4s1spa7z7c5wrj7yh9ph-disko-destroy-format-mount.drv' failed with exit code 1;
       last 13 log lines:
       >
       > In /nix/store/5sj8ippl51fazmsqizayzqbhzq4vqkjz-disko-destroy-format-mount line 130:
       >         IFS= read -r -s "$var"
       >                         ^----^ SC2229 (warning): This does not read 'var'. Remove $/${} for that, or use ${var?} to quiet.
       >
       >
       > In /nix/store/5sj8ippl51fazmsqizayzqbhzq4vqkjz-disko-destroy-format-mount line 140:
       >           [ "$password" = "$password_check" ]
       >                            ^-------------^ SC2154 (warning): password_check is referenced but not assigned.
       >
       > For more information:
       >   https://www.shellcheck.net/wiki/SC2154 -- password_check is referenced but ...
       >   https://www.shellcheck.net/wiki/SC2229 -- This does not read 'var'. Remove ...
       For full logs, run:
         nix log /nix/store/nwkn8awvj95a4s1spa7z7c5wrj7yh9ph-disko-destroy-format-mount.drv
error: 1 dependencies of derivation '/nix/store/r9fxfz6cfaya1ygs5g6836aqjy76g231-nixos-test-driver-disko-muradin-disko.drv' failed to build
error: 1 dependencies of derivation '/nix/store/3x7rqw691w7jlwnr1mmb8vb5jdbfps3h-vm-test-run-disko-muradin-disko.drv' failed to build
``