sculpt_manager: 'File_operation_queue' enhancement

This patch add the support needed for implementing on-target
system-update functionality. The new 'empty' method is required for the
two-step procedure of updating image-index files - removing the old
index, followed by downloading the most current one. It is used to the
detect the completion of the first step.

Issue #4744

repos/gems/src/app/sculpt_manager/model/file_operation_queue.h

@@ -32,19 +32,34 @@ struct Sculpt::File_operation_queue : Noncopyable
 
 		State state { State::PENDING };
 
-		enum class Type { REMOVE_FILE } type;
+		enum class Type { REMOVE_FILE, COPY_ALL_FILES } type;
 
-		Path const path;
+		Path const from { };
+		Path const path; /* destination */
 
 		Operation(Type type, Path const &path) : type(type), path(path) { }
 
+		Operation(Type type, Path const &from, Path const &to)
+		: type(type), from(from), path(to) { }
+
 		void gen_fs_tool_config(Xml_generator &xml) const
 		{
 			if (state != State::IN_PROGRESS)
 				return;
 
-			xml.node("remove-file", [&] () {
-				xml.attribute("path", path); });
+			switch (type) {
+
+			case Type::REMOVE_FILE:
+				xml.node("remove-file", [&] {
+					xml.attribute("path", path); });
+				break;
+
+			case Type::COPY_ALL_FILES:
+				xml.node("copy-all-files", [&] {
+					xml.attribute("from", from);
+					xml.attribute("to",   path); });
+				break;
+			}
 		}
 	};
 
@@ -64,7 +79,25 @@ struct Sculpt::File_operation_queue : Noncopyable
 		if (already_exists)
 			return;
 
-		new (_alloc) Registered<Operation>(_operations, Operation::Type::REMOVE_FILE, path);
+		new (_alloc) Registered<Operation>(_operations,
+		                                   Operation::Type::REMOVE_FILE, path);
+	}
+
+	void copy_all_files(Path const &from, Path const &to)
+	{
+		new (_alloc) Registered<Operation>(_operations,
+		                                   Operation::Type::COPY_ALL_FILES, from, to);
+	}
+
+	bool copying_to_path(Path const &path) const
+	{
+		bool result = false;
+		_operations.for_each([&] (Operation const &operation) {
+			if (operation.path == path)
+				if (operation.type == Operation::Type::COPY_ALL_FILES)
+					result = true; });
+
+		return result;
 	}
 
 	bool any_operation_in_progress() const
@@ -77,6 +110,13 @@ struct Sculpt::File_operation_queue : Noncopyable
 		return any_in_progress;
 	}
 
+	bool empty() const
+	{
+		bool result = true;
+		_operations.for_each([&] (Operation const &) { result = false; });
+		return result;
+	}
+
 	void schedule_next_operations()
 	{
 		/*