fix: Fixes updater failing in certain cases.

nixinfra/update.sh

@@ -1,15 +1,38 @@
-#!/usr/bin/env bash
-if [[ "$NIX_BUILD_ID" == "" ]]; then
+nix_bld_unset_err() {
   echo "ERROR: You have held a (potentially) broken install!"
   echo "NIX_BUILD_ID is not set (should be set by default!)"
   echo "Please set NIX_BUILD_ID manually. i.e:"
   echo "NIX_BUILD_ID=kitteh-node-1/agent updater"
   exit 1
+}
+
+if [[ "$NIX_BUILD_ID" == "" ]]; then
+  if [[ ! -f "/tmp/nixbuildid" ]]; then
+    nix_bld_unset_err
+  fi
+
+  source /tmp/nixbuildid
+
+  if [[ "$NIX_BUILD_ID" == "" ]]; then
+    nix_bld_unset_err
+  fi
 fi
 
 if [[ "$UID" != "0" ]]; then
+  # Hacky workaround for failing to read NIX_BUILD_ID when called like:
+  # ./update
+  # but this works:
+  # sudo ./update
+
+  echo "NIX_BUILD_ID=$NIX_BUILD_ID" > /tmp/nixbuildid
+  chmod +x /tmp/nixbuildid
+  
   sudo $0 $@
-  exit $?
+  STATUS_CODE=$?
+
+  rm -rf /tmp/nixbuildid
+
+  exit $STATUS_CODE
 fi
 
 pushd /etc/nixos 2> /dev/null > /dev/null