tests/test-gendoc-da.t

phabricator: allow specifying reviewers on phabsend

Sometimes people want to specify reviewer explicitly for a stack. The
webpage only allows changing reviewer for one revision at a time. This patch
adds a `--reviewer` flag to make it easier to specify reviewers.

Test Plan:
On a test Phabricator instance, enable `differential.allow-self-accept`,
assign myself as a reviewer and make sure it works. Also try an invalid
username and make sure it raises.

Differential Revision: https://phab.mercurial-scm.org/D38

#require docutils gettext

  $ $TESTDIR/check-gendoc da
  checking for parse errors