Display download count on project page

Here's the project usage hunk of drupalorg_project:

  // Usage stats.
  $total_usage = project_usage_get_project_total_usage($node->nid);
  if ($total_usage) {
    $label = t('Reported installs');
    $info[$label] = format_plural($total_usage,
      '<span class="count">1</span> site currently reports using this @project-type. <a href="/project/usage/!project-shortname">View usage statistics</a>.',
      '<span class="count">@count</span> sites currently report using this @project-type. <a href="/project/usage/!project-shortname">View usage statistics</a>.',
      array(
        '@project-type' => drupal_strtolower($project_type->label),
        '!project-shortname' => $node->project['uri'],
      )
    );
  }

And here's the relevant functions from project_usage module:

/**
 * Return the total usage data for a given project across all versions.
 *
 * @param $nid
 *   The project node ID.
 *
 * @return
 *   The total reported usage for all versions of the given project.
 */
function project_usage_get_project_total_usage($nid) {
  $active_tids = project_release_compatibility_list();
  static $total = array();
  if (empty($total[$nid])) {
    $total[$nid] = 0;
    foreach ($active_tids as $tid => $term_name) {
      $total[$nid] += project_usage_get_project_usage($nid, $tid);
    }
  }
  return $total[$nid];
}

/**
 * Return usage data for a given API version of a project.
 *
 * @param $nid
 *   The project node ID.
 * @param $tid
 *   The API compatibility taxonomy term ID to get usage for.
 *
 * @return
 *   The total reported usage for the given version of the given project.
 */
function project_usage_get_project_usage($nid, $tid) {
  static $usage = array();
  module_load_include('inc', 'project_usage', 'includes/date_api');
  if (empty($usage[$nid][$tid])) {
    $usage[$nid][$tid] = db_result(db_query("SELECT count FROM {project_usage_week_project} WHERE nid = %d AND tid = %d AND timestamp = %d", $nid, $tid, project_usage_get_current_active_week()));
  }
  return $usage[$nid][$tid];
}

/**
 * Return usage data for a given release.
 *
 * @param $nid
 *   The release node ID.
 *
 * @return
 *   The total reported usage for the given release.
 */
function project_usage_get_release_usage($nid) {
  static $usage = array();
  module_load_include('inc', 'project_usage', 'includes/date_api');
  if (empty($usage[$nid])) {
    $usage[$nid] = db_result(db_query("SELECT count FROM {project_usage_week_release} WHERE nid = %d AND timestamp = %d", $nid, project_usage_get_current_active_week()));
  }
  return $usage[$nid];
}

And the downloads are stored in the project_release_file table:

CREATE TABLE `project_release_file` (
  `fid` int(10) unsigned NOT NULL default '0',
  `nid` int(10) unsigned NOT NULL default '0',
  `filehash` varchar(32) NOT NULL default '',
  `weight` tinyint(4) NOT NULL default '0',
  `downloads` int(11) NOT NULL default '0',
  PRIMARY KEY  (`fid`),
  KEY `nid` (`nid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Followed up at #32124-33: Enable download statistics

One other caveat is that the download tracking only goes back as far as January 2009. We should make sure to note that next to the count.