From 4a252aa465c7a36268e8014674800e6d98a449e9 Mon Sep 17 00:00:00 2001
From: Kitsune Ral <Kitsune-Ral@users.sf.net>
Date: Sat, 8 Dec 2018 22:39:38 +0900
Subject: Omittable<>::merge<>

---
 lib/util.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/util.h b/lib/util.h
index 0066c03d..9c9a37ba 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -118,6 +118,22 @@ namespace QMatrixClient
                 _omitted = false;
                 return _value;
             }
+            /// Merge the value from another Omittable
+            /// \return true if \p other is not omitted and the value of
+            ///         the current Omittable was different (or omitted);
+            ///         in other words, if the current Omittable has changed;
+            ///         false otherwise
+            template <typename T1>
+            auto merge(const Omittable<T1>& other)
+                -> std::enable_if_t<std::is_convertible<T1, T>::value, bool>
+            {
+                if (other.omitted() ||
+                        (!_omitted && _value == other.value()))
+                    return false;
+                _omitted = false;
+                _value = other.value();
+                return true;
+            }
             value_type&& release() { _omitted = true; return std::move(_value); }
 
             operator value_type&() & { return editValue(); }
-- 
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