feat(web): keep unattended watcher alive at empty queue

my-tools/start_unattended.sh

@@ -9,6 +9,7 @@ SCHEDULER_PUSH_RETRIES="${WBV2_PUSH_RETRIES:-6}"
 WATCHDOG_INTERVAL="${WBV2_WATCHDOG_INTERVAL:-10}"
 WATCHDOG_RESTART_DELAY="${WBV2_WATCHDOG_RESTART_DELAY:-5}"
 AUTO_AUTHORIZE="${WBV2_AUTO_AUTHORIZE:-1}"
+WAIT_ON_EMPTY="${WBV2_WAIT_ON_EMPTY:-1}"
 
 # Keep repository evidence on disk while placing compiler/transient caches in
 # RAM. Eight compile jobs is the repository's stability limit.
@@ -46,9 +47,13 @@ start_scheduler() {
 start_watchdog() {
   local pid_file="$CONTROL_DIR/my-tools-watchdog.pid"
   local auto_authorize_args=()
+  local wait_on_empty_args=()
   if test "$AUTO_AUTHORIZE" != "0"; then
     auto_authorize_args+=(--auto-authorize)
   fi
+  if test "$WAIT_ON_EMPTY" != "0"; then
+    wait_on_empty_args+=(--wait-on-empty)
+  fi
   if test -f "$pid_file"; then
     local watchdog_pid
     watchdog_pid="$(tr -d '[:space:]' < "$pid_file")"
@@ -64,6 +69,7 @@ start_watchdog() {
     --max-iterations "$SCHEDULER_MAX_ITERATIONS" \
     --push-retries "$SCHEDULER_PUSH_RETRIES" \
     "${auto_authorize_args[@]}" \
+    "${wait_on_empty_args[@]}" \
     --commit --push \
     > "$CONTROL_DIR/my-tools-watchdog.stdout.log" 2>&1 < /dev/null &
   printf 'watchdog launch pid: %s\n' "$!"