R1:824f93462279

Diffusion - move commit parents query to conduit

Summary:
Ref T2784. Relatively complicated one as this bad boy is used in a repository daemon.

While testing, I noticed bugs in the expandshortname query stuff. Those variables are private to the parent class so they need some setX love.

Also, was unable to find links to the "before" stuff, but made them by hand by looking at some of these T2784 diffs, browsing a file at a specific revision, then hacking the "before" variable to be some known commit that…