feat: allow to declare disko-config relative to flake

cli.nix

@@ -1,10 +1,14 @@
 { pkgs ? import <nixpkgs> {}
 , mode ? "mount"
+, fromFlake ? null
 , diskoFile
 , ... }@args:
 let
-  disko = import ./. { inherit (pkgs) lib; };
-  diskFormat = import diskoFile;
+  disko = import ./. { };
+  diskFormat =
+    if fromFlake != null
+    then (builtins.getFlake fromFlake) + "/${diskoFile}"
+    else import diskoFile;
   diskoEval = if (mode == "create") then
     disko.createScript diskFormat pkgs
   else if (mode == "mount") then

disko

@@ -6,6 +6,9 @@ readonly libexec_dir="${0%/*}"
 # a file with the disko config
 declare disko_config
 
+# a flake uri, if present disko config is relative to the flake root
+declare from_flake
+
 # mount was chosen as the default mode because it's less destructive
 mode=mount
 nix_args=()
@@ -18,6 +21,8 @@ Options:
 
 * -m, --mode mode
   set the mode, either create or mount
+* -f, --flake uri
+  fetch the disko config relative to this flake's root
 * --arg name value
   pass value to nix-build. can be used to set disk-names for example
 * --argstr name value
@@ -43,6 +48,11 @@ while [[ $# -gt 0 ]]; do
       mode=$2
       shift
       ;;
+    -f | --flake)
+      from_flake="$2"
+      nix_args+=("--argstr" "fromFlake" "$2")
+      shift
+      ;;
     --argstr | --arg)
       nix_args+=("$1" "$2" "$3")
       shift
@@ -53,7 +63,7 @@ while [[ $# -gt 0 ]]; do
       exit 0
       ;;
     *)
-      if [ -z ${disko_config+x} ] && [ -e "$1" ]; then
+      if [ -z ${disko_config+x} ]; then
         disko_config=$1
       else
         showUsage
@@ -68,8 +78,16 @@ if ! ([[ $mode = "create" ]] || [[ $mode = "mount" ]]); then
   abort "mode must be either create or mount"
 fi
 
+if [[ -e "${disko_config}" ]]; then
+  nix_args+=("--arg" "diskoFile" "$disko_config")
+elif [[ -n "${from_flake+x}" ]]; then
+  nix_args+=("--argstr" "diskoFile" "$disko_config")
+else
+  abort "disko config must be an exising file of flake must be set"
+fi
+
 script=$(nix-build "${libexec_dir}"/cli.nix \
-  --arg diskoFile "$disko_config" \
+  --argstr diskoFile "$disko_config" \
   --argstr mode "$mode" \
   "${nix_args[@]}"
 )