Fix SetNamespace docs and behavior when namespace already exist

[lestrrat]

fixes #102

[guitarpawat]

I pulled your library and found a possible way to fix the current namespace prefix issue by using the same namespace pointer if it already exists.
I am not familiar with CGO, so I am not sure if this is the right way to do.

[guitarpawat]

Using the same namespace pointer if it already exists

Suggested change

	if oldNs, _ := clib.XMLSearchNs(doc, n, prefix); oldNs == 0 {
	// Namespace not found, create a new one
	ns, err := clib.XMLNewNs(n, uri, prefix)
	if err != nil {
	return err
	}
	if activateflag {
	if err := clib.XMLSetNs(n, wrapNamespaceNode(ns)); err != nil {
	return err
	}
	}
	}
	ns, _ := clib.XMLSearchNs(doc, n, prefix)
	if ns == 0 {
	// Namespace not found, create a new one
	ns, err = clib.XMLNewNs(n, uri, prefix)
	if err != nil {
	return err
	}
	}
	if activateflag {
	if err := clib.XMLSetNs(n, wrapNamespaceNode(ns)); err != nil {
	return err
	}
	}

[guitarpawat]

Add test to check namespace prefix

Suggested change

	})
	// root.Dump(true) should contains namespace prefix for Document
	count = strings.Count(dump, "ex:Document")
	require.Equal(t, 2, count, "expected Document to have 'ex' namespace prefix")
	// root.Dump(true) should contains namespace prefix for Test
	count = strings.Count(dump, "ex:Test")
	require.Equal(t, 2, count, "expected Test to have 'ex' namespace prefix")
	})

[guitarpawat]

Add test to check namespace prefix

Suggested change

	})
	// root.Dump(true) should contains namespace prefix for Document
	count = strings.Count(dump, "ex:Document")
	require.Equal(t, 2, count, "expected Document to have 'ex' namespace prefix")
	// root.Dump(true) should contains namespace prefix for Test
	count = strings.Count(dump, "ex:Test")
	require.Equal(t, 2, count, "expected Test to have 'ex' namespace prefix")
	})

[github-actions]

This PR is stale because it has been open 14 days with no activity. Remove stale label or comment or this will be closed in 14 days.

[github-actions]

This PR was closed because it has been stalled for 14 days with no activity. This does not mean your PR is rejected, but rather it is done to hide it from the view of the maintainers for the time being. Feel free to reopen if you have new comments or chnages that you would like to include.