feat(log): support verbosing logging

Author: Jim Zhang

Diff for: example/verbose.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+source "$(cd "${BASH_SOURCE[0]%/*}" && pwd)/../lib/oo-bootstrap.sh"
+
+import util/log
+
+namespace test/verbose
+VERBOSE=2
+
+Log::AddOutput test/verbose DEBUG
+
+Log "this log will be printed"
+V=2 Log "this log will be displayed"
+
+VERBOSE=1
+V=2 Log "this log will not be displayed"

Diff for: lib/util/log.sh

@@ -36,6 +36,12 @@ Log::DisableFilter() {
 }
 
 Log() {
+  # support verbosing logging
+  local V="${V:-0}"
+  if [[ $VERBOSE < $V ]]; then
+    return
+  fi
+
   local callingFunction="${FUNCNAME[1]}"
   local callingScript="${BASH_SOURCE[1]}"
   local scope