nixos/gitlab: Abort on error and use of unset variables

Default behavior is to continue executing the script even when one or
multiple steps fail. We want to abort early if any part of the
initialization fails to not run with a partially initialized state.

Default behavior also allows dereferencing non-existent variables,
potentially resulting in hard-to-find bugs.

nixos/modules/services/misc/gitlab.nix

@@ -608,6 +608,8 @@ in {
     # objects owners and extensions; for now we tack on what's needed
     # here.
     systemd.services.postgresql.postStart = mkAfter (optionalString databaseActuallyCreateLocally ''
+      set -eu
+
       $PSQL -tAc "SELECT 1 FROM pg_database WHERE datname = '${cfg.databaseName}'" | grep -q 1 || $PSQL -tAc 'CREATE DATABASE "${cfg.databaseName}" OWNER "${cfg.databaseUsername}"'
       current_owner=$($PSQL -tAc "SELECT pg_catalog.pg_get_userbyid(datdba) FROM pg_catalog.pg_database WHERE datname = '${cfg.databaseName}'")
       if [[ "$current_owner" != "${cfg.databaseUsername}" ]]; then
@@ -781,10 +783,14 @@ in {
         ExecStartPre = let
           preStartFullPrivileges = ''
             shopt -s dotglob nullglob
+            set -eu
+
             chown --no-dereference '${cfg.user}':'${cfg.group}' '${cfg.statePath}'/*
             chown --no-dereference '${cfg.user}':'${cfg.group}' '${cfg.statePath}'/config/*
           '';
           preStart = ''
+            set -eu
+
             cp -f ${cfg.packages.gitlab}/share/gitlab/VERSION ${cfg.statePath}/VERSION
             rm -rf ${cfg.statePath}/db/*
             rm -rf ${cfg.statePath}/config/initializers/*