Fix unnecessary-copy-initialization

> warning: the variable 'key' is copy-constructed from a const reference but is
only used as const reference; consider making it a const reference
[performance-unnecessary-copy-initialization]

Found by clang-tidy.

apps/openmw/mwgui/tooltips.cpp

@@ -650,7 +650,7 @@ namespace MWGui
 
     std::string ToolTips::getSoulString(const MWWorld::CellRef& cellref)
     {
-        std::string soul = cellref.getSoul();
+        const std::string& soul = cellref.getSoul();
         if (soul.empty())
             return std::string();
         const MWWorld::ESMStore &store = MWBase::Environment::get().getWorld()->getStore();
@@ -666,7 +666,7 @@ namespace MWGui
     {
         std::string ret;
         ret += getMiscString(cellref.getOwner(), "Owner");
-        const std::string factionId = cellref.getFaction();
+        const std::string& factionId = cellref.getFaction();
         if (!factionId.empty())
         {
             const MWWorld::ESMStore &store = MWBase::Environment::get().getWorld()->getStore();

apps/openmw/mwmechanics/magiceffects.cpp

@@ -137,7 +137,7 @@ namespace MWMechanics
     {
         if (this==&effects)
         {
-            MagicEffects temp (effects);
+            const MagicEffects& temp (effects);
             *this += temp;
             return *this;
         }

apps/wizard/inisettings.cpp

@@ -122,7 +122,7 @@ bool Wizard::IniSettings::writeFile(const QString &path, QTextStream &stream)
         QString section(fullKey.at(0));
         section.prepend(QLatin1Char('['));
         section.append(QLatin1Char(']'));
-        QString key(fullKey.at(1));
+        const QString& key(fullKey.at(1));
 
         int index = buffer.lastIndexOf(section);
         if (index == -1) {

components/detournavigator/navigatorutils.cpp

@@ -11,7 +11,7 @@ namespace DetourNavigator
         const auto navMesh = navigator.getNavMesh(agentHalfExtents);
         if (!navMesh)
             return std::nullopt;
-        const auto settings = navigator.getSettings();
+        const auto& settings = navigator.getSettings();
         const auto result = DetourNavigator::findRandomPointAroundCircle(navMesh->lockConst()->getImpl(),
             toNavMeshCoordinates(settings.mRecast, agentHalfExtents), toNavMeshCoordinates(settings.mRecast, start),
             toNavMeshCoordinates(settings.mRecast, maxRadius), includeFlags, settings.mDetour);
@@ -26,7 +26,7 @@ namespace DetourNavigator
         const auto navMesh = navigator.getNavMesh(agentHalfExtents);
         if (navMesh == nullptr)
             return std::nullopt;
-        const auto settings = navigator.getSettings();
+        const auto& settings = navigator.getSettings();
         const auto result = DetourNavigator::raycast(navMesh->lockConst()->getImpl(),
             toNavMeshCoordinates(settings.mRecast, agentHalfExtents), toNavMeshCoordinates(settings.mRecast, start),
             toNavMeshCoordinates(settings.mRecast, end), includeFlags, settings.mDetour);

components/esm/esmreader.cpp

@@ -70,7 +70,7 @@ void ESMReader::resolveParentFileIndices(const std::vector<ESMReader>& allPlugin
             const ESMReader& reader = allPlugins.at(i);
             if (reader.getFileSize() == 0)
                 continue;  // Content file in non-ESM format
-            const std::string candidate = reader.getName();
+            const std::string& candidate = reader.getName();
             std::string fnamecandidate = boost::filesystem::path(candidate).filename().string();
             if (Misc::StringUtils::ciEqual(fname, fnamecandidate)) {
                 index = i;