Consolidate querying of things which we can use git for-each-ref for

Summary: Ref T2230. This cleans up D7442, by using `git for-each-ref` everywhere we can, in a basically reasonable way.

Test Plan:
In bare and non-bare repositories:

  - Ran discovery with `bin/repository discover`;
  - listed branches on `/diffusion/X/`;
  - listed tags on `/diffusion/X/`;
  - listed tags, branches and refs on `/diffusion/rXnnnn`.

Reviewers: btrahan, avivey

Reviewed By: avivey

CC: aran

Maniphest Tasks: T2230

Differential Revision: https://secure.phabricator.com/D7447

src/applications/diffusion/data/DiffusionRepositoryRef.php

@@ -0,0 +1,36 @@
+<?php
+
+final class DiffusionRepositoryRef {
+
+  private $shortName;
+  private $commitIdentifier;
+  private $rawFields;
+
+  public function setRawFields(array $raw_fields) {
+    $this->rawFields = $raw_fields;
+    return $this;
+  }
+
+  public function getRawFields() {
+    return $this->rawFields;
+  }
+
+  public function setCommitIdentifier($commit_identifier) {
+    $this->commitIdentifier = $commit_identifier;
+    return $this;
+  }
+
+  public function getCommitIdentifier() {
+    return $this->commitIdentifier;
+  }
+
+  public function setShortName($short_name) {
+    $this->shortName = $short_name;
+    return $this;
+  }
+
+  public function getShortName() {
+    return $this->shortName;
+  }
+
+}