fix(report): use nix eval to list the components

This is less error prone than parsing the information from `nix flake
show`.

scripts/create-report.sh

@@ -7,24 +7,25 @@ util_path="${GITHUB_ACTION_PATH:-.}/scripts/utils.sh"
 # shellcheck source=scripts/utils.sh
 . "${util_path}"
 
-group 'Retrieving Flake information'
-flake_info=$(nix flake show --json --quiet --quiet)
-endgroup
-
 system=$(nix eval --impure --json --expr 'builtins.currentSystem')
 
-group 'Show Packages'
-packages=$(echo "$flake_info" | jq --raw-output --argjson system "$system" 'getpath(["packages", $system]) | select(. != null) | keys[]')
+# Extract the names of a flake attrset
+get_names() {
+  nix eval --json --apply builtins.attrNames "$1" 2>/dev/null | jq '.[]'
+}
+
+group "Show Packages for $system"
+packages=$(get_names .#packages."$system")
 [ -z "$packages" ] || log "$packages"
 endgroup
 
 group 'Show Home Manager Configurations'
-hmConfigs=$(echo "$flake_info" | jq --raw-output '.homeConfigurations | select(. != null) | keys[]')
+hmConfigs=$(get_names .#homeConfigurations)
 [ -z "$hmConfigs" ] || log "$hmConfigs"
 endgroup
 
 group 'Show NixOS Configurations'
-nixosConfigs=$(echo "$flake_info" | jq --raw-output '.nixosConfigurations | select(. != null) | keys[]')
+nixosConfigs=$(get_names .#nixosConfigurations)
 [ -z "$nixosConfigs" ] || log "$nixosConfigs"
 endgroup