TW-1906/#1919: sync sub-command is missing from task(1) manual page

- Thanks to rjc.

AUTHORS

@@ -321,3 +321,4 @@ suggestions:
   Martin Strunz
   Kai HTML
   Marc Richter
+  rjc

ChangeLog

@@ -63,6 +63,8 @@
           (thanks to Dan Callahan).
 - TW-1903 grammar error -- There are 1 local changes.
           (thanks to Eric Hymowitz).
+- TW-1906/#1919 sync sub-command is missing from task(1) manual page
+          (thanks to rjc).
 - TW-1910 unreachable statement
           (thanks to Martin Strunz).
 - TW-1930 Typo in help

doc/man/task.1.in

@@ -529,6 +529,25 @@ Shows statistics of the tasks defined by the filter.
 .B task <filter> summary
 Shows a report of aggregated task status by project.
 
+.TP
+.B task sync [init]
+The sync command synchronizes data with the Taskserver, if configured.
+
+The init subcommand should only ever be run once, and only on one client, because
+it sends all data to the Taskserver. This allows all the subsequent sync commands
+to only send small deltas.
+
+Note: If you use multiple sync clients, make sure this setting (which is the default)
+is on your primary client:
+
+  recurrence=on
+
+and on all other clients (this is not the default):
+
+  recurrence=off
+
+This is a workaround to avoid a recurrence bug that duplicates recurring tasks.
+
 .TP
 .B task <filter> tags
 Show a list of all tags used. Any special tags used are highlighted. Note that