Propagator: Recover from 'precondition failed' error

When we detect a precondition failed, it is possible that it is
because the etag in the database is wrong.  We must therefore not
read from the database on the next sync.  In order to avoid that, we
reset the etag of parent directories to invalid values

Fixes #1767

src/mirall/propagator_qnam.cpp

@@ -257,6 +257,12 @@ void PropagateUploadFileQNAM::slotPutFinished()
             errorString += QLatin1String(" (") + rx.cap(1) + QLatin1Char(')');
         }
 
+        if (_item._httpErrorCode == 412) {
+            // Precondition Failed:   Maybe the bad etag is in the database, we need to clear the
+            // parent folder etag so we won't read from DB next sync.
+            _propagator->_journal->avoidReadFromDbOnNextSync(_item._file);
+        }
+
         done(classifyError(err, _item._httpErrorCode), errorString);
         return;
     }

src/mirall/syncjournaldb.cpp

@@ -835,6 +835,28 @@ void SyncJournalDb::avoidRenamesOnNextSync(const QString& path)
     }
 }
 
+void SyncJournalDb::avoidReadFromDbOnNextSync(const QString& fileName)
+{
+    //Make sure that on the next sync, filName is not read from the DB but use the PROPFIND to
+    //get the info from the server
+    // We achieve that by clearing the etag of the parents directory recursively
+
+    QMutexLocker locker(&_mutex);
+
+    if( !checkConnect() ) {
+        return;
+    }
+
+    QSqlQuery query(_db);
+    // This query will match entries for whitch the path is a prefix of fileName
+    query.prepare("UPDATE metadata SET md5='_invalid_' WHERE ? LIKE(path||'/%') AND type == 2"); // CSYNC_FTW_TYPE_DIR == 2
+    query.bindValue(0, fileName);
+    if( !query.exec() ) {
+        qDebug() << "SQL error in avoidRenamesOnNextSync: "<< query.lastError().text();
+    } else {
+        qDebug() << query.executedQuery()  << fileName;
+    }
+}
 
 void SyncJournalDb::commit(const QString& context, bool startTrans)
 {

src/mirall/syncjournaldb.h

@@ -73,6 +73,12 @@ class OWNCLOUDSYNC_EXPORT SyncJournalDb : public QObject
     SyncJournalBlacklistRecord blacklistEntry( const QString& );
     void avoidRenamesOnNextSync(const QString &path);
 
+    /**
+     * Make sure that on the next sync, filName is not read from the DB but use the PROPFIND to
+     * get the info from the server
+     */
+    void avoidReadFromDbOnNextSync(const QString& fileName);
+
     bool postSyncCleanup( const QHash<QString, QString>& items );
 
     /* Because sqlite transactions is really slow, we encapsulate everything in big transactions