[c++/m] Add Source parentSource method

Adds parentSource method to the Source entity
on c++ and matlab side and adds a corresponding
test.

Author: mpsonntag

+nix/Source.m

@@ -48,6 +48,10 @@
             retObj = nix.Utils.open_entity(obj, ...
                 'Source::openSource', id_or_name, @nix.Source);
         end;
-        
+
+        function retObj = parent_source(obj)
+            retObj = nix.Utils.fetchObj('Source::parentSource', ...
+                obj.nix_handle, @nix.Source);
+        end
     end;
 end

nix_mx.cc

@@ -243,6 +243,7 @@ void mexFunction(int            nlhs,
             .reg("setType", SETTER(const std::string&, nix::Source, type))
             .reg("setDefinition", SETTER(const std::string&, nix::Source, definition))
             .reg("setNoneDefinition", SETTER(const boost::none_t, nix::Source, definition))
+            .reg("parentSource", GETTER(nix::Source, nix::Source, parentSource))
             .reg("sourceCount", GETTER(nix::ndsize_t, nix::Source, sourceCount));
 
         classdef<nix::Tag>("Tag", methods)

tests/TestSource.m

@@ -18,6 +18,7 @@
     funcs{end+1} = @test_has_source;
     funcs{end+1} = @test_open_source;
     funcs{end+1} = @test_source_count;
+    funcs{end+1} = @test_parent_source;
     funcs{end+1} = @test_set_metadata;
     funcs{end+1} = @test_open_metadata;
 end
@@ -190,3 +191,18 @@
     f = nix.File(fullfile(pwd, 'tests', fileName), nix.FileMode.ReadOnly);
     assert(f.blocks{1}.sources{1}.has_source(nestedID));
 end
+
+%% Test: Get parent source
+function [] = test_parent_source( varargin )
+    fileName = fullfile(pwd, 'tests', 'testRW.h5');
+    f = nix.File(fileName, nix.FileMode.Overwrite);
+    b = f.create_block('sourcetest', 'nixBlock');
+    sourceName1 = 'testSource1';
+    sourceName2 = 'testSource2';
+    s1 = b.create_source(sourceName1, 'nixSource');
+    s2 = s1.create_source(sourceName2, 'nixSource');
+    s3 = s2.create_source('testSource3', 'nixSource');
+
+    assert(strcmp(s3.parent_source.name, sourceName2));
+    assert(strcmp(s2.parent_source.name, sourceName1));
+end