Merge branch 'better-priority-sorting' into 'master'

Better priority sorting

Closes #28754

See merge request !9938

2 files changed, 25 insertions, 7 deletions

diff --git a/doc/user/project/labels.md b/doc/user/project/labels.md
index cf1d9cbe69c..8ec7adad172 100644
--- a/doc/user/project/labels.md
+++ b/doc/user/project/labels.md
@@ -65,7 +65,7 @@ issues and merge requests assigned to each label.
 >   https://gitlab.com/gitlab-org/gitlab-ce/issues/18554.
 
 Prioritized labels are like any other label, but sorted by priority. This allows
-you to sort issues and merge requests by priority.
+you to sort issues and merge requests by label priority.
 
 To prioritize labels, navigate to your project's **Issues > Labels** and click
 on the star icon next to them to put them in the priority list. Click on the
@@ -77,9 +77,13 @@ having their priority set to null.
 
 ![Prioritize labels](img/labels_prioritize.png)
 
-Now that you have labels prioritized, you can use the 'Priority' filter in the
-issues or merge requests tracker. Those with the highest priority label, will
-appear on top.
+Now that you have labels prioritized, you can use the 'Priority' and 'Label
+priority' filters in the issues or merge requests tracker.
+
+The 'Label priority' filter puts issues with the highest priority label on top.
+
+The 'Priority' filter sorts issues by their soonest milestone due date, then by
+label priority.
 
 ![Filter labels by priority](img/labels_filter_by_priority.png)
 
@@ -156,4 +160,3 @@ mouse over the label in the issue tracker or wherever else the label is
 rendered.
 
 ![Label tooltips](img/labels_description_tooltip.png)
-
diff --git a/doc/workflow/milestones.md b/doc/workflow/milestones.md
index dff36899aec..37afe553e55 100644
--- a/doc/workflow/milestones.md
+++ b/doc/workflow/milestones.md
@@ -1,13 +1,28 @@
 # Milestones
 
-Milestones allow you to organize issues and merge requests into a cohesive group, optionally setting a due date. 
+Milestones allow you to organize issues and merge requests into a cohesive group, optionally setting a due date.
 A common use is keeping track of an upcoming software version. Milestones are created per-project.
 
 ![milestone form](milestones/form.png)
 
 ## Groups and milestones
 
-You can create a milestone for several projects in the same group simultaneously. 
+You can create a milestone for several projects in the same group simultaneously.
 On the group's milestones page, you will be able to see the status of that milestone across all of the selected projects.
 
 ![group milestone form](milestones/group_form.png)
+
+## Special milestone filters
+
+In addition to the milestones that exist in the project or group, there are some
+special options available when filtering by milestone:
+
+* **No Milestone** - only show issues or merge requests without a milestone.
+* **Upcoming** - show issues or merge request that belong to the next open
+  milestone with a due date, by project. (For example: if project A has
+  milestone v1 due in three days, and project B has milestone v2 due in a week,
+  then this will show issues or merge requests from milestone v1 in project A
+  and milestone v2 in project B.)
+* **Started** - show issues or merge requests from any milestone with a start
+  date less than today. Note that this can return results from several
+  milestones in the same project.