refactor: improve distro detection reliability in install.sh

[DatRatVS]

Problem

The original distro detection relied solely on checking for the presence of package manager binaries (pacman, dnf, apt) and a single NixOS-specific file. This approach had two issues:

• Derivative distros (e.g. AlmaLinux, Rocky, Manjaro, EndeavourOS) were not explicitly handled, so detection could fail or return an unexpected value depending on the environment.
• Package manager checks are inherently fragile — some distros ship with multiple package managers (and users can install additional ones) or have binaries available that don't represent the primary one.

Solution

c45eec9: Rewrote detect_distro() to use /etc/os-release as the primary detection method, which is the modern Linux standard and available on all major distributions. The ID field is matched case-insensitively against known distro families:

Detected as	Covers
arch	arch, manjaro, endeavouros
fedora	fedora, rhel, centos, rocky, almalinux, alma
debian	debian, ubuntu, mint, pop
nixos	nixos

The original package manager / file-based checks are kept as a fallback for edge cases where /etc/os-release is absent.

Testing

Tested via Docker across 5 distributions:

Distro	Expected	Result
ubuntu:latest	debian	debian
debian:latest	debian	debian
fedora:latest	fedora	fedora
almalinux:latest	fedora	fedora
archlinux:latest	arch	arch

Test Scripts

• test.sh

for distro in ubuntu:latest debian:latest fedora:latest almalinux:latest archlinux:latest; do
    echo "=== $distro ==="
    docker run --rm -v "$PROJECT/detect_distro.sh:/test.sh" "$distro" bash /test.sh
done

• detect_distro.sh (which is a cut down snippet from original install.sh)

GREEN='\033[0;32m' BLUE='\033[0;34m' YELLOW='\033[1;33m' RED='\033[0;31m' NC='\033[0m'
log_info() { echo -e "${BLUE}ℹ  $1${NC}" >&2; }
has_cmd() { command -v "$1" >/dev/null 2>&1; }

detect_distro() {
    if [[ -f /etc/os-release ]]; then
        local id
        id=$(. /etc/os-release && echo "${ID,,}")
        case "$id" in
            nixos)               echo "nixos"   ;;
            arch | manjaro | endeavouros) echo "arch" ;;
            fedora | rhel | centos | rocky | almalinux | alma) echo "fedora" ;;
            debian | ubuntu | mint | pop)  echo "debian" ;;
            *)                   echo "$id"     ;;
        esac
        return 0
    else
        #
        # Fallbacks to original Ambxst detection method
        #
        [[ -f /etc/NIXOS ]] && echo "nixos" && return
        has_cmd pacman && echo "arch" && return
        has_cmd dnf && echo "fedora" && return
        has_cmd apt && echo "debian" && return
        echo "unknown"
    fi
}

DISTRO=$(detect_distro)
log_info "Detected: $DISTRO"

Results