Remove dead Jenkins code and support `arc diff --preview` in RocksDB

Summary:
Two changes here:

- Remove dead Jenkins related code which is no longer relevant.
- Support `arc diff --preview`. Currently it doesn't work because a step which applies a diff assumes that a revision has been created. Which in case of `--preview` isn't. Therefore diff can't be applied and validation fails. Solution is to use `--nocommit` because for validation purposes performing a commit isn't necessary.

Test Plan:
- Current changes are submitted using `arc diff --preview`.
- All the pre-commit verification tests passed.

Reviewers: kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: leveldb, andrewkr, jtolmer, dhruba

Differential Revision: https://reviews.facebook.net/D59571

arcanist_util/config/FacebookArcanistConfiguration.php

@@ -10,7 +10,6 @@ class FacebookArcanistConfiguration extends ArcanistConfiguration {
                                  ArcanistBaseWorkflow $workflow,
                                  $error_code) {
     if ($command == 'diff' && !$workflow->isRawDiffSource()) {
-      $this->startTestsInJenkins($workflow);
       $this->startTestsInSandcastle($workflow);
     }
   }
@@ -72,7 +71,7 @@ class FacebookArcanistConfiguration extends ArcanistConfiguration {
     $patch = array(
       "name" => "Patch " . $diffID,
       "shell" => "HTTPS_PROXY=fwdproxy:8080 arc --arcrc-file ~/.arcrc "
-                  . "patch --diff " . $diffID,
+                  . "patch --nocommit --diff " . $diffID,
       "user" => "root"
     );
 
@@ -185,22 +184,4 @@ class FacebookArcanistConfiguration extends ArcanistConfiguration {
     // Ask phabricator to display it on the diff UI
     $this->postURL($diffID, $sandcastle_url[1]);
   }
-
-  //////////////////////////////////////////////////////////////////////
-  /* Send off builds to jenkins */
-  function startTestsInJenkins($workflow) {
-    $diffID = $workflow->getDiffID();
-    if ($diffID === null) {
-      return;
-    }
-
-    $results = $workflow->getTestResults();
-    if (!$results) {
-      return;
-    }
-
-    $url = "https://ci-builds.fb.com/view/rocksdb/job/rocksdb_diff_check/"
-               ."buildWithParameters?token=AUTH&DIFF_ID=$diffID";
-    system("curl --noproxy '*' \"$url\" > /dev/null 2>&1");
-  }
 }

arcanist_util/unit_engine/FacebookFbcodeUnitTestEngine.php

@@ -7,15 +7,11 @@
 class FacebookFbcodeUnitTestEngine extends ArcanistBaseUnitTestEngine {
 
   public function run() {
-    // Here we create a new unit test "jenkins_async_test" and promise we'll
-    // update the results later.
-    // Jenkins updates the results using `arc call-conduit
-    // differential.updateunitresults` call. If you change the name here, also
-    // make sure to change the name in Jenkins script that updates the test
-    // result -- they have to be the same.
+      // For a call to `arc call-conduit differential.updateunitresults` to
+      // succeed we need at least one entry here.
       $result = new ArcanistUnitTestResult();
-    $result->setName("jenkins_async_test");
-    $result->setResult(ArcanistUnitTestResult::RESULT_POSTPONED);
+      $result->setName("dummy_placeholder_entry");
+      $result->setResult(ArcanistUnitTestResult::RESULT_PASS);
       return array($result);
   }
 }