Feature/graph transactions

[no-reply]

This implements write transactions for RDF::Graph, partially fulfilling #269.

Transactional read scoped to a Graph remains to be implemented.

[gkellogg]

LGTM other than comment.

[no-reply]

A fix is in for false graph names via 0c1294a.

See also: 3a6762e.

Tests are, likewise, fixed at: ruby-rdf/rdf-spec#56

[no-reply]

One thing to note is that these changes work slightly differently from inserting/deleting statements on a RDF::Graph directly.

graph << statement will overwrite the graph_name. In a transaction context, we will retain an existing graph_name, but add the Graph#graph_name when one isn't present for the statement.

This is roughly how things worked with Changeset in 1.1.x. If we want things to look like regular graph insertion (where, e.g. graph1 << graph2 works) we really need to rethink things.

[no-reply]

Apart from my note about graph_name I think this is ready.

It doesn't close #269 until Transactional graph read is done.

[gkellogg]

If we want things to look like regular graph insertion (where, e.g. graph1 << graph2 works) we really need to rethink things.

Maybe create an issue to track this. It is fairly useful to do an insert of an enumerable, as is done elsewhere.

[no-reply]

@gkellogg you can insert enumerables as usual. The potential sticking point is that if one enumerable emits graph_name for its statements, the Graph will accept it in a Transaction, but replace it otherwise.

An issue is open at: #278