Redmine

This patch adds a new setting for handling start and due dates, which I here call "partially independent", which was initially proposed in #5490, #5490-91, to be more specific.

I implemented this as part of a new feature request in #34609. This issue now provides a patch to add an option set start and due date, as well as done ratio and priority to "partially derived".

As the proposed way of submitting a patch seems to be to add another issue ("I have a patch to add X" - these need to be filed into the Issue Tracker, as stated in https://www.redmine.org/boards/4/topics/15134) I add this new issue, which basically contains the patch from #34609-6. More implementation details can also be found in #34609.

I hope I am doing this right!?

Why is this new setting useful?

There are currently two ways of handling start date and due date of parent tickets and subtasks: "Independent" and "Derived".

When set to "Independent", the parent issue does not care about the dates set in the subtasks.
One can define start and due date for a parent ticket and it stays like this, which is good for planning tasks for a certain time.
However, when adding subtasks their dates do not influence the dates of the parent task. A subtask can set (or get delayed ) to be completely outside the time slot of the parent task. This means work from a subtask taking longer is not reflecting back into the parent task.

When set to "Derived", the start and due date of the parent task are completely controlled by the subtasks. So if you plan a parent task to start in January and be done in May and then add a shorter subtask, e.g. starting February and ending already in March, the parent task will suddenly change its planned dates to the ones defined in the subtask. The initial planning is lost.

The implementation proposed in #34609 adds a third option, bringing together the best of both already existing options.
The parent tasks dates are independent of the subtasks dates, as long as the subtasks fit within the parent task.
If subtask get delayed beyond the due date of the parent task the delay gets transferred over to the parent task, but as long as subtasks stay within the confines of the parent task the parent task keeps its initial dates and can be independently edited. Basically subtask only extend the time of the parent task, if required, but no longer shrink it.

This makes hierarchical planning of projects and task more useful.

Similarly the partially derived option for done ratio and priority allow the done ratio of the parent task to be lower than the done ratio derived from its subtasks and the priority to be higher than the highest priority derived from the subtasks.

I would like to ask the developers to take a look at the patch and possibly at #34609, as well as include the patch into the core, or let me know if some more work is required.