libsync: Get the maxParallel from the server

If the server can't cope with parallel upload, it can advertise it
in the capabilities secion

Issue #2743
Need owncloud/core#13628

src/libsync/owncloudpropagator.cpp

@@ -28,6 +28,7 @@
 #include "configfile.h"
 #include "utility.h"
 #include <json.h>
+#include "account.h"
 
 #ifdef Q_OS_WIN
 #include <windef.h>
@@ -46,11 +47,16 @@ namespace OCC {
 /* The maximum number of active job in parallel  */
 int OwncloudPropagator::maximumActiveJob()
 {
-    static int max = qgetenv("OWNCLOUD_MAX_PARALLEL").toUInt();
-    if (!max) {
-        max = 3; //default
+    if (_maxParallel <= 0) {
+        _maxParallel = qgetenv("OWNCLOUD_MAX_PARALLEL").toUInt();
+        if (_maxParallel <= 0) {
+            _maxParallel = _account->capabilities().value("files").toMap().value("maxparallels").toInt();
+        }
+        if (_maxParallel <= 0) {
+            _maxParallel = 3; // default value if the server says "O" or did not specify anything
+        }
     }
-    return max;
+    return _maxParallel;
 }
 
 /** Updates or creates a blacklist entry for the given item.

src/libsync/owncloudpropagator.h

@@ -266,6 +266,7 @@ class OwncloudPropagator : public QObject {
             , _activeJobs(0)
             , _anotherSyncNeeded(false)
             , _account(account)
+            , _maxParallel(0)
     { }
 
     void start(const SyncFileItemVector &_syncedItems);
@@ -339,6 +340,7 @@ private slots:
 private:
 
     AccountPtr _account;
+    int _maxParallel;
 
     /** Stores the time since a job touched a file. */
     QHash<QString, QElapsedTimer> _touchedFiles;