Bug #1273

- #1273 Query with negative relative date differs greatly from absolute date
  in past (thanks to John West).

src/Duration.cpp

@@ -368,6 +368,8 @@ bool Duration::valid (const std::string& input)
   Nibbler n (lower_input);
   n.getNumber (value);
 
+  // Negative values are valid, but do not need to complicate the validation
+  // check.
   if (value < 0.0)
     value = -value;
 

src/E9.cpp

@@ -185,7 +185,10 @@ void E9::eval (const Task& task, std::vector <Arg>& value_stack)
           {
             Duration dur (operand._raw);
             Date now;
-            now += (int)(time_t) dur;
+            if (dur.negative ())
+              now -= (int)(time_t) dur;
+            else
+              now += (int)(time_t) dur;
             operand._value  = now.toEpochString ();
           }
           else

src/commands/Command.cpp

@@ -463,7 +463,7 @@ void Command::modify_task (
   std::string& description)
 {
   // Utilize Task::modify
-  task.modify(arguments, description);
+  task.modify (arguments, description);
 }
 
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