add flake and default .nix files; add agenix command

pkgs/agenix.sh

@@ -0,0 +1,49 @@
+#! /usr/bin/env nix-shell
+#! nix-shell -i bash -p age yq-go moreutils
+
+while test $# -gt 0; do
+  case "$1" in
+    -h|--help)
+      echo "$package - attempt to capture frames"
+      echo " "
+      echo "$package [options] application [arguments]"
+      echo " "
+      echo "options:"
+      echo "-h, --help                show brief help"
+      echo "-a, --action=ACTION       specify an action to use"
+      echo "-o, --output-dir=DIR      specify a directory to store output in"
+      exit 0
+      ;;
+    -a)
+      shift
+      if test $# -gt 0; then
+        export PROCESS=$1
+      else
+        echo "no process specified"
+        exit 1
+      fi
+      shift
+      ;;
+    --action*)
+      export PROCESS=`echo $1 | sed -e 's/^[^=]*=//g'`
+      shift
+      ;;
+    -o)
+      shift
+      if test $# -gt 0; then
+        export OUTPUT=$1
+      else
+        echo "no output dir specified"
+        exit 1
+      fi
+      shift
+      ;;
+    --output-dir*)
+      export OUTPUT=`echo $1 | sed -e 's/^[^=]*=//g'`
+      shift
+      ;;
+    *)
+      break
+      ;;
+  esac
+done