Introduce synchronize merge method

* Create history-based merging that keeps older data in history instead of discarding or deleting it
* Extract merge logic into the Merger class
* Allows special merge behavior
* Improve handling of deletion and changes on groups
* Enable basic change tracking while merging
* Prevent unintended timestamp changes while merging
* Handle differences in timestamp precision
* Introduce comparison operators to allow for more sophisticated comparisons (ignore special properties, ...)
* Introduce Clock class to handle datetime across the app

Merge Strategies:
* Default (use inherited/fallback method)
* Duplicate (duplicate conflicting nodes, apply all deletions)
* KeepLocal (use local values, but apply all deletions)
* KeepRemote (use remote values, but apply all deletions)
* KeepNewer (merge history only)
* Synchronize (merge history, newest value stays on top, apply all deletions)

1 files changed, 58 insertions, 0 deletions

diff --git a/src/core/Clock.h b/src/core/Clock.h
new file mode 100644
index 000000000..8f81b0961
--- /dev/null
+++ b/src/core/Clock.h
@@ -0,0 +1,58 @@
+/*
+ *  Copyright (C) 2018 KeePassXC Team <team@keepassxc.org>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 2 or (at your option)
+ *  version 3 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef KEEPASSXC_CLOCK_H
+#define KEEPASSXC_CLOCK_H
+
+#include <QDateTime>
+#include <QSharedPointer>
+
+class Clock
+{
+public:
+    static QDateTime currentDateTimeUtc();
+    static QDateTime currentDateTime();
+
+    static uint currentSecondsSinceEpoch();
+
+    static QDateTime serialized(const QDateTime& dateTime);
+
+    static QDateTime datetimeUtc(int year, int month, int day, int hour, int min, int second);
+    static QDateTime datetime(int year, int month, int day, int hour, int min, int second);
+
+    static QDateTime datetimeUtc(qint64 msecSinceEpoch);
+    static QDateTime datetime(qint64 msecSinceEpoch);
+
+    static QDateTime parse(const QString& text, Qt::DateFormat format = Qt::TextDate);
+    static QDateTime parse(const QString& text, const QString& format);
+
+    virtual ~Clock();
+
+protected:
+    Clock();
+    virtual QDateTime currentDateTimeUtcImpl() const;
+    virtual QDateTime currentDateTimeImpl() const;
+
+    static void resetInstance();
+    static void setInstance(Clock* clock);
+    static const Clock& instance();
+
+private:
+    static QSharedPointer<Clock> m_instance;
+};
+
+#endif // KEEPASSX_ENTRY_H