perf(rename): cache fileExists results in PropagateLocalRename::start

PropagateLocalRename::start was calling FileSystem::fileExists up to
five times across the same three paths in a row. Each call is a
filesystem stat. Cache the three results into local bools and reuse
them.

Side benefit: the Q_ASSERT and the two qCDebug log lines now match
the bool values used in fileAlreadyMoved, eliminating the chance of
the assert and the log disagreeing if the filesystem state changes
mid-function.

Signed-off-by: Qoole <2862661+qoole@users.noreply.github.com>

Author: qoole

src/libsync/propagatorjobs.cpp

@@ -349,7 +349,10 @@ void PropagateLocalRename::start()
     const auto targetFile = propagator()->fullLocalPath(_item->_renameTarget);
     const auto originalFile = propagator()->fullLocalPath(_item->_originalFile);
 
-    const auto fileAlreadyMoved = (!FileSystem::fileExists(originalFile) || !FileSystem::fileExists(existingFile))&& FileSystem::fileExists(targetFile);
+    const auto origExists = FileSystem::fileExists(originalFile);
+    const auto existingExists = FileSystem::fileExists(existingFile);
+    const auto targetExists = FileSystem::fileExists(targetFile);
+    const auto fileAlreadyMoved = (!origExists || !existingExists) && targetExists;
     auto pinState = OCC::PinState::Unspecified;
     if (!fileAlreadyMoved) {
         auto pinStateResult = vfs->pinState(propagator()->adjustRenamedPath(_item->_file));
@@ -361,9 +364,9 @@ void PropagateLocalRename::start()
     // if the file is a file underneath a moved dir, the _item->file is equal
     // to _item->renameTarget and the file is not moved as a result.
     qCDebug(lcPropagateLocalRename) << _item->_file << _item->_renameTarget << _item->_originalFile << previousNameInDb << (fileAlreadyMoved ? "original file has already moved" : "original file is still there");
-    qCDebug(lcPropagateLocalRename()) << (FileSystem::fileExists(originalFile) ? "original file exists" : "original file is missing") << originalFile << _item->_originalFile;
-    qCDebug(lcPropagateLocalRename()) << (FileSystem::fileExists(existingFile) ? "existing file exists" : "existing file is missing") << existingFile << previousNameInDb;
-    Q_ASSERT(FileSystem::fileExists(propagator()->fullLocalPath(_item->_originalFile)) || FileSystem::fileExists(existingFile));
+    qCDebug(lcPropagateLocalRename()) << (origExists ? "original file exists" : "original file is missing") << originalFile << _item->_originalFile;
+    qCDebug(lcPropagateLocalRename()) << (existingExists ? "existing file exists" : "existing file is missing") << existingFile << previousNameInDb;
+    Q_ASSERT(origExists || existingExists);
     if (_item->_file != _item->_renameTarget) {
         propagator()->reportProgress(*_item, 0);
         qCDebug(lcPropagateLocalRename) << "MOVE " << existingFile << " => " << targetFile;