Normalize file names before using them as keys

On macOS the filenames on disk are stored in NFD form. When the original
filename on the server was in NFC form, the filenames wouldn't match,
and a MOVE or DELETE+PUT would be triggered.

This changes converts all filenames to NFC form during local discovery.

src/libsync/discovery.cpp

@@ -80,9 +80,13 @@ void ProcessDirectoryJob::process()
         RemoteInfo serverEntry;
         LocalInfo localEntry;
     };
+
+    // The key for the `entries` mapping is the NFC form of the filename. This is done to prevent
+    // NFC->NFD or NFD->NFC conversions done by `QFile` and/or the underlying local filesystem.
     std::map<QString, Entries> entries;
     for (auto &e : _serverNormalQueryEntries) {
-        entries[e.name].serverEntry = std::move(e);
+        // Keep the name on the server as-is, but use the NFC form as the key
+        entries[e.name.normalized(QString::NormalizationForm_C)].serverEntry = std::move(e);
     }
     _serverNormalQueryEntries.clear();
 
@@ -93,7 +97,7 @@ void ProcessDirectoryJob::process()
             if (rec.isVirtualFile() && isVfsWithSuffix()) {
                 name = chopVirtualFileSuffix(name);
             }
-            auto &dbEntry = entries[name].dbEntry;
+            auto &dbEntry = entries[name.normalized(QString::NormalizationForm_C)].dbEntry;
             dbEntry = rec;
             setupDbPinStateActions(dbEntry);
         })) {
@@ -102,6 +106,7 @@ void ProcessDirectoryJob::process()
     }
 
     for (auto &e : _localNormalQueryEntries) {
+        e.name = e.name.normalized(QString::NormalizationForm_C);
         entries[e.name].localEntry = e;
     }
     if (isVfsWithSuffix()) {
@@ -140,8 +145,16 @@ void ProcessDirectoryJob::process()
     for (const auto &f : entries) {
         const auto &e = f.second;
 
-        PathTuple path;
-        path = _currentFolder.addName(e.nameOverride.isEmpty() ? f.first : e.nameOverride);
+        QString name;
+        if (!e.nameOverride.isEmpty()) {
+            name = e.nameOverride;
+        } else if (!e.serverEntry.name.isEmpty()) {
+            // IF there is a name on the server, take that, as it hasn't been normalized.
+            name = e.serverEntry.name;
+        } else {
+            name = f.first;
+        }
+        PathTuple path = _currentFolder.addName(name);
 
         if (isVfsWithSuffix()) {
             // Without suffix vfs the paths would be good. But since the dbEntry and localEntry