If "branch" is provided to "diffusion.branchquery", use it as the "<pattern>" argument to "git branch --contains ..."

Summary:
Ref T13151. See PHI720. If you want to test if commit X appears on specific branch Y, `git branch --contains X -- Y` is faster than (effectively) `git branch --contains X | grep Y`.

Since this call has a "branch" parameter anyway, use it as the pattern argument if provided.

Test Plan:
  - Called the API method with no parameters, got all branches.
  - Called the API method with `master`, got just master.
  - Called the API method with `maste*`, got master. This behavior is not officially supported and may change in the future.
  - Viewed a commit, still saw all branches.
    - Grepped for `diffusion.branchquery` and verified that no remaining callsites pass a default "branch" parameter.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13151

Differential Revision: https://secure.phabricator.com/D19499

src/applications/diffusion/controller/DiffusionCommitBranchesController.php

@@ -22,6 +22,7 @@ final class DiffusionCommitBranchesController extends DiffusionController {
         array(
           'contains' => $drequest->getCommit(),
           'limit' => $branch_limit + 1,
+          'branch' => null,
         )));
 
     $has_more_branches = (count($branches) > $branch_limit);