feat: also search for nested flake.nix files (fixes #12)

nix/package.nix

@@ -19,8 +19,16 @@ writeShellScriptBin "agenix" ''
     echo '  generate                Automatically generates secrets that have generators'
   }
 
-  USER_FLAKE_DIR=$(git rev-parse --show-toplevel 2>/dev/null || pwd) \
+  USER_GIT_TOPLEVEL=$(realpath -e "$(git rev-parse --show-toplevel 2>/dev/null || pwd)") \
     || die "Could not determine current working directory. Something went very wrong."
+  USER_FLAKE_DIR=$(realpath -e "$(pwd)") \
+    || die "Could not determine current working directory. Something went very wrong."
+
+  # Search from $(pwd) upwards to $USER_GIT_TOPLEVEL until we find a flake.nix
+  while [[ ! -e "$USER_FLAKE_DIR/flake.nix" ]] && [[ "$USER_FLAKE_DIR" != "$USER_GIT_TOPLEVEL" ]] && [[ "$USER_FLAKE_DIR" != "/" ]]; do
+    USER_FLAKE_DIR="$(dirname "$USER_FLAKE_DIR")"
+  done
+
   [[ -e "$USER_FLAKE_DIR/flake.nix" ]] \
     || die "Could not determine location of your project's flake.nix. Please run this at or below your main directory containing the flake.nix."
   cd "$USER_FLAKE_DIR"