engine: tell peers about detached recurrence exceptions

The Maemo 5 calendar backend does not support UID/RECURRENCE-ID
semantic. This is problematic in combination with peers which rely on
that to override the main recurring event on specific recurrences,
because the Maemo 5 calendar will show duplicates.

Fixing this inside the calendar backend is hard because it doesn't get
to see all related events at once. The engine has the same
problem. Therefore a workaround is used:
- backends which have that unified access to all related events
  add special X-SYNCEVOLUTION-EXDATE-DETACHED properties to the
  main event which correspond to the exceptions represented by
  detached recurrences, in addition to the regular EXDATE; the
  backend must set the HAVE-SYNCEVOLUTION-EXDATE-DETACHED rule when
  using PARSETEXTWITHPROFILE()
- the engine parses the special property (only if the
  HAVE-SYNCEVOLUTION-EXDATE-DETACHED rule is active!) and stores
  the values in the EXDATES_DETACHED field
- this gets passed between SyncEvolution instances in a local
  or SyncML sync
- another SyncEvolution backend can request to get either
  X-SYNCEVOLUTION-EXDATE-DETACHED or regular EXDATE properties
  by setting the HAVE-[SYNCEVOLUTION-]EXDATE-DETACHED rules

The Maemo 5 backend needs to set HAVE-EXDATE-DETACHED. This means that
importing events will add additional EXDATEs which will be sent back
when updating events inside the calendar app, but that is okay. They
are merely redundant.

src/syncevo/MapSyncSource.h

@@ -184,6 +184,12 @@ class SubSyncSource : virtual public SyncSourceBase
      */
     virtual std::string getSubDescription(const string &mainid, const string &subid) = 0;
 
+    /**
+     * Called after MapSyncSource already populated the info structure.
+     */
+    virtual void updateSynthesisInfo(SynthesisInfo &info,
+                                     XMLConfigFragments &fragments) {}
+
  private:
     MapSyncSource *m_parent;
 };
@@ -273,6 +279,13 @@ class MapSyncSource :
     /* TestingSyncSource */
     virtual void removeAllItems();
 
+ protected:
+    virtual void getSynthesisInfo(SynthesisInfo &info,
+                                  XMLConfigFragments &fragments) {
+        TestingSyncSource::getSynthesisInfo(info, fragments);
+        m_sub->updateSynthesisInfo(info, fragments);
+    }
+
  private:
     boost::shared_ptr<SubSyncSource> m_sub;
     /** escape / in uid with %2F, so that splitMainIDValue() and splitLUID() can use / as separator */

src/syncevo/configs/datatypes/10calendar-fieldlist.xml

@@ -56,6 +56,20 @@
       <!-- for events -->
       <field name="EXDATES" array="yes" type="timestamp" compare="never"/>
 
+      <!-- EXDATEs for detached recurrences: meant to be used for the
+           RECURRENCE-IDs of all detached recurrences.
+
+           Can be ignored when dealing with only iCalendar 2.0 aware
+           peers, because these EXDATEs are implied for detached
+           recurrences and don't have to be specified explicitly. Can
+           be used to create additional EXDATEs for non-iCalendar 2.0
+           peers. For that, EXDATES_DETACHED must be populated by the
+           backend creating the parent event, because the engine
+           itself doesn't have the necessary
+           information. X-SYNCEVOLUTION-EXDATE-DETACHED can be used
+           for that in serialized calendar events. -->
+      <field name="EXDATES_DETACHED" array="yes" type="timestamp" compare="never"/>
+
       <field name="ORIGSTART" array="no" type="timestamp" compare="never"/>
       <field name="SEQNO" array="no" type="integer" compare="never"/>
 

src/syncevo/configs/datatypes/11calendar-profile.xml

@@ -394,6 +394,23 @@
             <position field="EXDATES" repeat="array" increment="1" minshow="0"/>
           </property>
 
+          <!-- parse X-SYNCEVOLUTION-EXDATE-DETACHED, but never encode it like this except internally -->
+          <property name="X-SYNCEVOLUTION-EXDATE-DETACHED" delayedparsing="1" mandatory="no"
+                    show="no" rule="HAVE-SYNCEVOLUTION-EXDATE-DETACHED">
+            <value field="EXDATES_DETACHED"/>
+            <parameter name="TZID" default="no" show="yes">
+              <value field="EXDATES_DETACHED" conversion="TZID"/>
+            </parameter>
+            <position field="EXDATES_DETACHED" repeat="array" increment="1" minshow="0"/>
+          </property>
+          <!-- encode as normal EXDATE when backend asks for it -->
+          <property name="EXDATE" show="no" rule="HAVE-EXDATE-DETACHED" mandatory="no">
+            <value field="EXDATES_DETACHED"/>
+            <parameter name="TZID" default="no" show="yes">
+              <value field="EXDATES_DETACHED" conversion="TZID"/>
+            </parameter>
+            <position field="EXDATES_DETACHED" repeat="array" increment="1" minshow="0"/>
+          </property>
 
           <property name="DTEND" suppressempty="yes" delayedparsing="1">
             <value field="DTEND" conversion="autoenddate"/>

src/syncevo/configs/remoterules/00_have_exdate_detached.xml

@@ -0,0 +1 @@
+    <subrule name="HAVE-EXDATE-DETACHED"/>

src/syncevo/configs/remoterules/00_have_syncevolution_exdate_detached.xml

@@ -0,0 +1 @@
+    <subrule name="HAVE-SYNCEVOLUTION-EXDATE-DETACHED"/>

src/syncevo/configs/remoterules/00_syncevolution.xml

@@ -2,6 +2,8 @@
       <manufacturer>Patrick Ohly</manufacturer>
       <model>SyncEvolution</model>
 
+      <include rule="HAVE-SYNCEVOLUTION-EXDATE-DETACHED"/>
+
       <include rule="HAVE-EVOLUTION-UI-SLOT"/>
       <!-- Merging between SyncEvolution instances is expected to work
            well, so allow the engine to update items on both