Implement explicit build step ordering in Harbormaster

Summary: This implements support for explicitly marking the sequence of build steps.  Users can now drag and re-order build steps in plans, and artifact dependencies are re-calculated so that if you move "Run Command" before "Lease Host", the "Run Command" step has it's artifact setting cleared and thus the step becomes invalid.

Test Plan: Re-ordered build steps and observed dependencies being correctly recalculated.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T1049

Differential Revision: https://secure.phabricator.com/D7715

resources/sql/patches/20131205.buildsteporder.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_harbormaster.harbormaster_buildstep
+ADD COLUMN sequence INT UNSIGNED NOT NULL;

resources/sql/patches/20131205.buildstepordermig.php

@@ -0,0 +1,41 @@
+<?php
+
+$table = new HarbormasterBuildPlan();
+$conn_w = $table->establishConnection('w');
+$viewer = PhabricatorUser::getOmnipotentUser();
+
+// Since HarbormasterBuildStepQuery has been updated to handle the
+// correct order, we can't use the built in database access.
+
+foreach (new LiskMigrationIterator($table) as $plan) {
+  $planname = $plan->getName();
+  echo "Migrating steps in {$planname}...\n";
+
+  $rows = queryfx_all(
+    $conn_w,
+    "SELECT id, sequence FROM harbormaster_buildstep ".
+    "WHERE buildPlanPHID = %s ".
+    "ORDER BY id ASC",
+    $plan->getPHID());
+
+  $sequence = 1;
+  foreach ($rows as $row) {
+    $id = $row['id'];
+    $existing = $row['sequence'];
+    if ($existing != 0) {
+      echo "  - {$id} (already migrated)...\n";
+      continue;
+    }
+    echo "  - {$id} to position {$sequence}...\n";
+    queryfx(
+      $conn_w,
+      "UPDATE harbormaster_buildstep ".
+      "SET sequence = %d ".
+      "WHERE id = %d",
+      $sequence,
+      $id);
+    $sequence++;
+  }
+}
+
+echo "Done.\n";