Fix from vs. continue

[blackwinter]

Recent MediaWiki versions (>= 1.19?) don't return @apfrom anymore. Instead, @apcontinue is returned in the response body.

This is inherently untestable with FakeMediaWiki and may not work on older MediaWiki versions. But testing against a live instance shows the effect:

# before:
MediaWiki::Gateway.new('https://en.wikipedia.org/w/api.php').list('Media').size #=> 500

# after:
MediaWiki::Gateway.new('https://en.wikipedia.org/w/api.php').list('Media').size #=> 2373

[jpatokal]

Otherwise cool, but I'd prefer not to break backward compatibility. Could you tweak the XPath to match either? I don't think ReXML supports (@apfrom|@apcontinue), since that's XPath 2, but something along the lines of @*[name()='apfrom' or name()='apcontinue'] should do the trick.

[blackwinter]

I can do that. In that case, however, I'd like to extract the logic that deals with continuing a query into a shared method. There's a lot of duplication and adding more logic doesn't help the fact at all. Would you agree and, if so, should it take place in this pull request or should I open a new one?

Also, backlinks and contributions are already continue-only. Should they be changed, too?

For future reference, MediaWiki API 2.0 is going to introduce a new "continue" syntax. At some point this library probably needs to take differing API capabilities into account.

[jpatokal]

Sounds good to me, feel free to add to this pull request. And the more fixes the merrier ;)

API 2.0 is most likely to be somebody else's problem...

[blackwinter]

Finished first pass. Still need to add documentation and do some more testing. Should be ready to push some time tomorrow.

(Turns out that #56 isn't settled yet, though. More on that later.)

[blackwinter]

Done: b489c94. Please let me know if you have any comments or want me to change anything.

[jpatokal]

Sweet, that's so much better than before. Thanks a million!