Add optional chart_end_date setting

This new setting allows you to change the end date of the chart
without affecting the slope of the ideal burndown line.

This is useful for showing tasks that were completed after the official
end of a sprint.

Author: thehale

README.md

@@ -88,6 +88,7 @@ This allows the `.gitignore` to exclude your `config.json` from being accidental
 |----------|---------|
 | `sprint_start_date` | The first day of the sprint formatted as `YYYY-MM-DD`. <br/><br/> Must be entered here since GitHub Project Boards don't have an assigned start/end date. <br/><br/> Example: `2021-10-08` |
 | `sprint_end_date` | The last day of the sprint formatted as `YYYY-MM-DD`. <br/><br/> Must be entered here since GitHub Project Boards don't have an assigned start/end date. <br/><br/> Example: `2021-10-21` |
+| `chart_end_date` | (OPTIONAL) The last day to show on the burndown chart formatted as `YYYY-MM-DD`. <br/><br/> Used to change the end date of the chart without affecting the slope of the ideal burndown line (e.g. to show tasks that were completed after the official end of a sprint). <br/><br/> Example: `2021-10-24` |
 | `points_label` | (OPTIONAL) The prefix for issue labels containing the point value of the issue. Removing this prefix must leave just an integer. If set to `null`, the burndown chart will count open issues instead of points.<br/><br/> Example: `Points: ` (with the space) |
 
 #### Organization Projects

src/github_projects_burndown_chart/chart/burndown.py

@@ -13,21 +13,26 @@ def __init__(self, project: Project):
             config['settings']['sprint_start_date'])
         self.end_date_utc: datetime = parse_to_utc(
             config['settings']['sprint_end_date'])
+        self.chart_end_date_utc: datetime = parse_to_utc(
+            config['settings']['chart_end_date']) \
+                if config['settings'].get('chart_end_date') else None
 
         self.project: Project = project
 
     def render(self):
+        end_date = self.chart_end_date_utc if self.chart_end_date_utc else self.end_date_utc
         outstanding_points_by_day = self.project.outstanding_points_by_date(
             self.start_date_utc,
-            self.end_date_utc)
+            end_date)
         # Load date dict for priority values with x being range of how many days are in sprint
         x = list(range(len(outstanding_points_by_day.keys())))
         y = list(outstanding_points_by_day.values())
+        sprint_days = (self.end_date_utc - self.start_date_utc).days
 
         # Plot point values for sprint along xaxis=range yaxis=points over time
         plt.plot(x, y)
         plt.axline((x[0], self.project.total_points),
-                   slope=-(self.project.total_points/(len(y)-1)),
+                   slope=-(self.project.total_points/(sprint_days)),
                    color="green",
                    linestyle=(0, (5, 5)))