flake: Improve service preStart

flake.nix

@@ -77,7 +77,7 @@
                   '';
                 };
                 mode = mkOption {
-                  type = types.str;
+                  type = types.enum [ "hardlink" "symlink" "move" "copy" ];
                   default = "hardlink";
                   description = ''
                     Organization mode, one of [ hardlink symlink move copy ].
@@ -100,10 +100,11 @@
                 wantedBy = [
                   "default.target"
                 ];
-                preStart = if !sync.skipFullSync then (''
+                preStart = ''
                   mkdir -p ${sync.target}
+                '' + (if !sync.skipFullSync then (''
                   photocatalog -source ${sync.source} -target ${sync.target} -mode ${sync.mode} ${if sync.overwrite then "-overwrite" else ""}
-                '') else null;
+                '') else null);
                 script = "photocatalog -source ${sync.source} -target ${sync.target} -skip-full-sync -watch -mode ${sync.mode} ${if sync.overwrite then "-overwrite" else ""}";
                 serviceConfig = {
                   Type="simple";