move ensureZfsMounts

overlays.nix

@@ -0,0 +1,33 @@
+final: prev: {
+  ensureZfsMounts = prev.writeShellApplication {
+    name = "zfsEnsureMounted";
+    runtimeInputs = with prev; [
+      zfs
+      gnugrep
+      gawk
+      coreutils
+    ];
+
+    text = ''
+      #!/bin/sh -x
+
+      if [[ "$#" -eq "0" ]]; then
+         echo "no arguments passed"
+         exit 1
+      fi
+
+      TARGETS=$(echo "$@" | sort | uniq)
+      MOUNTED=$(zfs list -o mountpoint,mounted -H | awk '$2 == "yes" {print $1}' | sort | uniq)
+      NUM_MATCHED=$(echo "$MOUNTED" | grep -Ec "$(echo "$@" | tr ' ' '\|')") # does not properly handle paths with strings
+      if [[ "$NUM_MATCHED" -eq "$#" ]]; then
+         exit 0
+      fi
+
+      FOUND=$(printf "%s\n%s" "$TARGETS" "$MOUNTED" | sort | uniq -c | awk '$1 == "2" {print $2}' | sort)
+      MISSING=$(printf "%s\n%s" "$FOUND" "$TARGETS" | sort | uniq -u | sort)
+
+      echo "FAILURE, missing: $MISSING" 1>&2
+      exit 1
+    '';
+  };
+}