[clang-tidy] Use .empty instead of comparing size

Found with readability-container-size-empty

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/feedback.cpp

@@ -208,8 +208,8 @@ std::string taskInfoDifferences (
     if (name              != "uuid" &&
         name              != "modified" &&
         before.get (name) != after.get (name) &&
-        before.get (name) != "" &&
-        after.get (name)  != "")
+        !before.get (name).empty() &&
+        !after.get (name).empty())
     {
       if (name == "depends")
       {
@@ -245,10 +245,10 @@ std::string renderAttribute (const std::string& name, const std::string& value,
     Column* col = Context::getContext ().columns[name];
     if (col                    &&
         col->type () == "date" &&
-        value != "")
+        !value.empty())
     {
       Datetime d ((time_t)strtol (value.c_str (), nullptr, 10));
-      if (format == "")
+      if (format.empty())
         return d.toString (Context::getContext ().config.get ("dateformat"));
 
       return d.toString (format);
@@ -379,7 +379,7 @@ void feedback_unblocked (const Task& task)
     for (auto& i : blocked)
     {
       auto blocking = dependencyGetBlocking (i);
-      if (blocking.size () == 0)
+      if (blocking.empty())
       {
         if (i.id)
           std::cout << format ("Unblocked {1} '{2}'.",
@@ -402,7 +402,7 @@ void feedback_unblocked (const Task& task)
 ///////////////////////////////////////////////////////////////////////////////
 void feedback_backlog ()
 {
-  if (Context::getContext ().config.get ("taskd.server") != "" &&
+  if (!Context::getContext ().config.get ("taskd.server").empty() &&
       Context::getContext ().verbose ("sync"))
   {
     int count = 0;
@@ -423,7 +423,7 @@ std::string onProjectChange (Task& task, bool scope /* = true */)
   std::stringstream msg;
   std::string project = task.get ("project");
 
-  if (project != "")
+  if (!project.empty())
   {
     if (scope)
       msg << format ("The project '{1}' has changed.", project)