Displays FQDN and flake commit hash with timestamp on login.
Templates can override with their own MOTD via mkDefault.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Convert remaining writeShellScript usages to writeShellApplication for
shellcheck validation and strict bash options.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Adds a helper script deployed to all hosts for testing feature branches.
Usage: nixos-rebuild-test <action> <branch>
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>