ReviewBoard and our workflow

[Eric Snow]

Steps for a review of a PR:

1. create pull request in github
2. run "rbt post" while at your branch to create a review request [1][2]
3. open the review request in your browser and "publish" it [3]
4. add a comment to the PR with a link to the review request
5. address reviews until you get a "Ship It!"
6. add a $$merge$$ comment to the PR

Both github and ReviewBoard support various triggers/hooks and both
have robust HTTP APIs.  So we should be able to automate those steps
(e.g. PR -> review request, "ship it" -> $$merge$$).  However, I don't
see that automation as a prerequisite for switching over to
ReviewBoard.

Updating an existing review request:
1. run "rbt post -u" (or the explicit "rbt post -r #")
2. open the review request in your browser and "publish" it [3]

FYI, Reviewboard supports chaining review requests.  Run rbt post
--parent <parent branch>.

I'll be updating the contributing doc relative to ReviewBoard (i.e.
with the above info) once we settle in with the new tool.

-eric

[1] Make sure your branch is based on upstream master.  Otherwise this
will not work right.
[2] Reviewboard links revision IDs to review requests.  So if you
already have a review request for a particular revision (e.g. your
branch), then "rbt post" will fail.  Use "rbt post -u" or "rbt post -r
#" instead.
[3] rbt post has some options you should consider using:
  - automatically publish the review request: rbt post --publish (or -p)
  - open a browser window with the new review request: rbt post --open (or -o)