Changed configuration option name and added documentation.

doc/man/taskrc.5.in

@@ -540,6 +540,12 @@ Taskwarrior supports command aliases. This alias provides an alternate name
 any of the commands. Several commands you may use are actually aliases -
 the 'history' report, for example, or 'export'.
 
+.TP
+.B burndown.cumulative=0
+May be "1" or "0", and controls the behaviour of the burndown command. When set 
+to 1, it sums up all completed tasks, otherwise they only get plotted in the 
+interval where the task was completed. Defaults to 1.
+
 .SS DATES
 
 .TP

src/commands/CmdBurndown.cpp

@@ -235,7 +235,17 @@ void Chart::scan (std::vector <Task>& tasks)
   Datetime now;
 
   time_t epoch;
-  bool cumulative = !Context::getContext ().config.getBoolean ("burndown.nc");
+  auto& config = Context::getContext ().config;
+  bool cumulative;
+  if (config.has ("burndown.cumulative"))
+  {
+    cumulative = config.getBoolean ("burndown.cumulative");
+  }
+  else
+  {
+    cumulative = true;
+  }
+
   for (auto& task : tasks)
   {
     // The entry date is when the counting starts.

test/burndown.t

@@ -66,7 +66,7 @@ class TestBurndownCommand(TestCase):
 
     def test_burndown_daily_non_cumulative(self):
         """Ensure burndown.daily in non-cumulative mode generates a chart"""
-        self.t.config("burndown.nc", True)
+        self.t.config("burndown.cumulative", False)
 		  code, out, err = self.t("burndown.daily")
         self.assertIn("Daily Burndown", out)
         self.assertIn(".", out)