[PATCH 09 of 10] phabricator: avoid calling differential.getrawdiff

[Jun Wu]

Excerpts from Augie Fackler's message of 2017-07-05 18:29:30 -0400:
> Oy. I'm not in love with having to clone their enum here. How stable
> can we assume these values are, given that you had to slurp them out
> of the arcanist source and not some API documentation?

git log --follow -p shows they never got changed since the first commit of
the repo [1]. There were zero new enums got added. Given the code history
and the fact that changing things here will break existing arcanist client
too, I think the enums are pretty stable.

Talking about documentation, the formal Phabricator API documentation is
very limited - most APIs only have first level type information for input
parameters.  There is almost zero text about nested parameters or output
parameters for APIs like differential.query [2]. So the source code is the
only available documentation.

Note: "differential.query" is marked as "Frozen", but arcanist is still
using it and it seems to be the only way to get the dependency information.

[1]: https://secure.phabricator.com/rARC2e73916fa20456af6b737c1208bfa3da0cc679ec
[2]: https://phab.mercurial-scm.org/conduit/method/differential.query/