GH-1060 update tweaks

* download to multimc folder hierarchy
* use rename, not copy
* keep backup after update
* clean previous backup before update
* it's not 'copy', it's 'replace'

logic/updater/DownloadTask.cpp

@@ -27,8 +27,8 @@
 namespace GoUpdate
 {
 
-DownloadTask::DownloadTask(Status status, QObject *parent)
-	: Task(parent)
+DownloadTask::DownloadTask(Status status, QString target, QObject *parent)
+	: Task(parent), m_updateFilesDir(target)
 {
 	m_status = status;
 

logic/updater/DownloadTask.h

@@ -30,7 +30,12 @@ class DownloadTask : public Task
 	Q_OBJECT
 
 public:
-	explicit DownloadTask(Status status, QObject* parent = 0);
+	/**
+	 * Create a download task
+	 *
+	 * target is a template - XXXXXX at the end will be replaced with a random generated string, ensuring uniqueness
+	 */
+	explicit DownloadTask(Status status, QString target, QObject* parent = 0);
 
 	/// Get the directory that will contain the update files.
 	QString updateFilesDir();

logic/updater/GoUpdate.h

@@ -68,7 +68,7 @@ struct Operation
 {
 	static Operation CopyOp(QString fsource, QString fdest, int fmode=0644)
 	{
-		return Operation{OP_COPY, fsource, fdest, fmode};
+		return Operation{OP_REPLACE, fsource, fdest, fmode};
 	}
 	static Operation DeleteOp(QString file)
 	{
@@ -84,7 +84,7 @@ struct Operation
 	//! Specifies the type of operation that this is.
 	enum Type
 	{
-		OP_COPY,
+		OP_REPLACE,
 		OP_DELETE,
 	} type;