Improve UX for repository updates

Summary:
Fixes T5926. Fixes T5830. Ref T4767. Users currently sometimes have a hard time understanding repository update frequencies. This is compounded by aggressive backoff and incorrect backoff while importing repositories.

  - Don't back off while importing repositories. This prevents us from hanging at 99.99% for inactive repositories while waiting for the next update.
  - Back off less aggressively in general, and even more gradually during the first 3 days. This should make behavior around weekends better.
  - Show update frequency in the UI.
  - Provide an explicit "update now" button to call `diffusion.looksoon` in a more user-friendly way.
  - Document how backoff policies work and how to adjust behavior.

Test Plan:
  - Ran `bin/phd debug pulllocal` and verified backoff worked correctly from debugging output.
  - Clicked "Update Now" to get a hint, reloaded page to see it update.
  - Read documentation.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4767, T5830, T5926

Differential Revision: https://secure.phabricator.com/D10323

src/applications/diffusion/controller/DiffusionRepositoryEditMainController.php

@@ -207,6 +207,14 @@ final class DiffusionRepositoryEditMainController
       ->setHref($this->getRepositoryControllerURI($repository, 'edit/basic/'));
     $view->addAction($edit);
 
+    $edit = id(new PhabricatorActionView())
+      ->setIcon('fa-refresh')
+      ->setName(pht('Update Now'))
+      ->setWorkflow(true)
+      ->setHref(
+        $this->getRepositoryControllerURI($repository, 'edit/update/'));
+    $view->addAction($edit);
+
     $activate = id(new PhabricatorActionView())
       ->setHref(
         $this->getRepositoryControllerURI($repository, 'edit/activate/'))
@@ -280,6 +288,10 @@ final class DiffusionRepositoryEditMainController
       pht('Status'),
       $this->buildRepositoryStatus($repository));
 
+    $view->addProperty(
+      pht('Update Frequency'),
+      $this->buildRepositoryUpdateInterval($repository));
+
     $description = $repository->getDetail('description');
     $view->addSectionHeader(pht('Description'));
     if (!strlen($description)) {
@@ -942,14 +954,16 @@ final class DiffusionRepositoryEditMainController
               ->setNote($message->getParameter('message')));
           return $view;
         case PhabricatorRepositoryStatusMessage::CODE_OKAY:
+          $ago = (PhabricatorTime::getNow() - $message->getEpoch());
           $view->addItem(
             id(new PHUIStatusItemView())
               ->setIcon(PHUIStatusItemView::ICON_ACCEPT, 'green')
               ->setTarget(pht('Updates OK'))
               ->setNote(
                 pht(
-                  'Last updated %s.',
-                  phabricator_datetime($message->getEpoch(), $viewer))));
+                  'Last updated %s (%s ago).',
+                  phabricator_datetime($message->getEpoch(), $viewer),
+                  phutil_format_relative_time_detailed($ago))));
           break;
       }
     } else {
@@ -1020,12 +1034,34 @@ final class DiffusionRepositoryEditMainController
         id(new PHUIStatusItemView())
           ->setIcon(PHUIStatusItemView::ICON_UP, 'indigo')
           ->setTarget(pht('Prioritized'))
-          ->setNote(pht('This repository will be updated soon.')));
+          ->setNote(pht('This repository will be updated soon!')));
     }
 
     return $view;
   }
 
+  private function buildRepositoryUpdateInterval(
+    PhabricatorRepository $repository) {
+
+    $smart_wait = $repository->loadUpdateInterval();
+
+    $doc_href = PhabricatorEnv::getDoclink(
+      'Diffusion User Guide: Repository Updates');
+
+    return array(
+      phutil_format_relative_time_detailed($smart_wait),
+      " \xC2\xB7 ",
+      phutil_tag(
+        'a',
+        array(
+          'href' => $doc_href,
+          'target' => '_blank',
+        ),
+        pht('Learn More')),
+    );
+  }
+
+
   private function buildMirrorActions(
     PhabricatorRepository $repository) {