VisualEditor/Backlog design

Decisions from planning meeting:
 * 1) Make the minimum number of changes to the VE Phabricator data necessary to produce:
 * 2) A stack-ranked backlog suitable for discussion and planning by most stakeholders
 * 3) The current and half to all of the next activity period (month?) should be fully stack-ranked
 * 4) The top 100 items/4 months of work should be stack-ranked to an accuracy of 25%.
 * 5) No other stack-ranking required; i.e., everything else could be unordered.
 * 6) A Product Burnup chart
 * 7) Don't (yet) try to do anything with orthogonal categorization of VE tasks (for example, don't try to tag all mobile tasks vs all desktop tasks, and/or all security vs all performance).  May come back to this later but not needed yet.
 * 8) Don't try to create a new project to contain a full stack-ranked list of all VE bugs (well, stack-ranked from 1-100).
 * 9) Reason 1: huge amount of Phab spam if we bulk-move 1300+ active and 3000+ closed tasks.
 * 10) Reason 2: Don't explicitly need it yet
 * 11) Do create tranches in order to organize the backlog.
 * 12) A tranche is an ordered set of all Stories and Epics (Tasks, in Phab) which the VE team intends to complete prior to all Stories and Epics in all lower-ranked tranches.
 * 13) For now, each tranche is intended to address a group of related issues.  (I.e., each tranche is effectively the top-priority tasks from a set of all tasks within a category, but the full list of all tasks in each category is not yet explicitly documented within Phab) The specific tranches planned are
 * 14) Fix anything that would block making VE available to more editors, or community acceptance thereof (empty for now)
 * 15) Demo of mobile version of VisualEditor
 * 16) Language-related improvements
 * 17) usability improvements to link inspector
 * 18) Tranches are implemented as columns within the VisualEditor project in Phabricator.
 * 19) As a tranche is completed, it is hidden but not deleted/emptied.
 * 20) VisualEditor shall always have an open Tranche 0, defined as "Interrupt", tasks which are urgent enough to jump ahead of all other planned work.
 * 21) Tranche 0 will also be stack-ranked.
 * 22) Tranche 0 will include (among other things) critical bugs for Wikitext, VisualEditor, and any other projects the VE team is responsible for.
 * 23) Logically, therefore, work on Tranches 1+ will only occur when Tranche 0 is empty or when the VE team is sufficiently staffed to have capacity available after engaging with all Tranche 0 tasks.
 * 24) The existing VisualEditor columns (of the form "Next Up:"  in Phabricator may serve as a card mapping area for items before they are assigned up to a tranche or down to the unordered lower backlog.
 * 25) The complete, stack-ranked list of VisualEditor tasks may therefore be derived from this algorithm:
 * 26) All open tasks in Tranche 0, in "natural order" as stored on the Phabricator board
 * 27) All open tasks in Tranche 1, in natural order
 * 28) All open tasks in Tranche 2, in natural order, etc.
 * 29) All open tasks in any "Next Up" columns, in no order (no order with columns and no order between columns)
 * 30) All open tasks in To Triage and in Backlog, in no order
 * 31) We will try to construct a Product burnup from a Phab data dump of this arrangement and refine the plan if that is not possible
 * 1) We will try to construct a Product burnup from a Phab data dump of this arrangement and refine the plan if that is not possible

= Open questions =
 * What are we doing with the Doing column?
 * move those tasks back into Tranches? (or treat that as tranche -1, and then stop using it after current tasks are done)
 * keep it? Then how does it relate to tranches?
 * What are we doing with the Done column?
 * stop using it after current tasks are done
 * How to generate estimates?
 * who does it?
 * which tasks need to be estimated?
 * are there homogeneous groups of tasks that can be assigned the average estimate from a subset?
 * How do we tie this explicitly to goals/OKRs?
 * Do we move OKRs into Phab?
 * How do we link Tasks to OKRs?
 * What is an activity period? A monthish?
 * How much of the backlog has to be well-ordered to have a realistic plan 4-6 months out?
 * can we do any ordering outside of the top hundred?
 * will we use the priority field for priority (and if so, how will it interact with the stack-ranking), or for severity, or for something else?