With this post, I'd like to submit org-conflict, a new Org add-on, to
the community for enjoyment, scrutiny and feedback.

Org-conflict aims to help Org agenda users prevent creating scheduling
conflicts.  If you use the agenda for calendar purposes, you might
benefit from validating timestamps before you commit them.

My own demand for conflict-free timestamps arose from using Org as the
back end of an iCalendar client I created for VM which exports Org
entries.  Most people who send me meeting requests use MS Outlook and
I got envious when I saw that Outlook informs them immediately of any
scheduling conflict when it processes incoming iCalendar data.
Initially, org-conflict was intended just as a Lisp predicate called
from the VM presentation buffer.  Adding an interactive mode, so that
it could be used on regular Org timestamps, was fairly easy.  Having
then added conflict resolution, I thought this might have enough
functionality to count as an Org add-on.

So here it is as the attached org-conflict.el, tested with Org 9.0 and
9.2.  Its implementation is "pure Org" and relies only on code that is
loaded anyway when Org is running.

Instead of posting a longish message to this list, I opted to explain
org-conflict in the attached FAQ document, of course a .org file.  The
added benefit being that the document is a self-contained demo.
Following the guided tour, you know after a couple of minutes
interaction if this package is for you.

If this is all tl;dr, here's org-conflict in brief:

 - compares a test time/timestamp/-range against 'org-agenda-files.
   Eligible timestamps in there are event-type, ie. contain a
   time-of-day and encode a duration

 - detects overlaps ("conflicts"), computes a resolution

 - supports intervals between events ("coffee breaks")

 - supports virtual ranges (end time is before start time)
   
 - customizable levels of automation

 - designed to be put on the C-c C-c hook, makes timestamps magic
 
 - dedicated interactive and non-interactive modes

Please let me know if this package is remotely useful, completely
misses the point or has crippling bugs and oversights.

Regards,

Thomas