Index: src/__phutil_library_map__.php
===================================================================
--- src/__phutil_library_map__.php
+++ src/__phutil_library_map__.php
@@ -902,10 +902,14 @@
     'HarbormasterCommandBuildStepImplementation' => 'applications/harbormaster/step/HarbormasterCommandBuildStepImplementation.php',
     'HarbormasterConduitAPIMethod' => 'applications/harbormaster/conduit/HarbormasterConduitAPIMethod.php',
     'HarbormasterController' => 'applications/harbormaster/controller/HarbormasterController.php',
+    'HarbormasterCustomFieldRepository' => 'applications/harbormaster/customfield/HarbormasterCustomFieldRepository.php',
     'HarbormasterDAO' => 'applications/harbormaster/storage/HarbormasterDAO.php',
     'HarbormasterHTTPRequestBuildStepImplementation' => 'applications/harbormaster/step/HarbormasterHTTPRequestBuildStepImplementation.php',
     'HarbormasterLeaseHostBuildStepImplementation' => 'applications/harbormaster/step/HarbormasterLeaseHostBuildStepImplementation.php',
     'HarbormasterLeaseWorkingCopyBuildStepImplementation' => 'applications/harbormaster/step/HarbormasterLeaseWorkingCopyBuildStepImplementation.php',
+    'HarbormasterLeaseWorkingCopyFromBuildableBuildStepImplementation' => 'applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromBuildableBuildStepImplementation.php',
+    'HarbormasterLeaseWorkingCopyFromRepositoryBuildStepImplementation' => 'applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromRepositoryBuildStepImplementation.php',
+    'HarbormasterLeaseWorkingCopyFromURLBuildStepImplementation' => 'applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromURLBuildStepImplementation.php',
     'HarbormasterLintMessagesController' => 'applications/harbormaster/controller/HarbormasterLintMessagesController.php',
     'HarbormasterLintPropertyView' => 'applications/harbormaster/view/HarbormasterLintPropertyView.php',
     'HarbormasterManagePlansCapability' => 'applications/harbormaster/capability/HarbormasterManagePlansCapability.php',
@@ -4407,10 +4411,14 @@
     'HarbormasterCommandBuildStepImplementation' => 'HarbormasterBuildStepImplementation',
     'HarbormasterConduitAPIMethod' => 'ConduitAPIMethod',
     'HarbormasterController' => 'PhabricatorController',
+    'HarbormasterCustomFieldRepository' => 'PhabricatorStandardCustomFieldPHIDs',
     'HarbormasterDAO' => 'PhabricatorLiskDAO',
     'HarbormasterHTTPRequestBuildStepImplementation' => 'HarbormasterBuildStepImplementation',
     'HarbormasterLeaseHostBuildStepImplementation' => 'HarbormasterBuildStepImplementation',
     'HarbormasterLeaseWorkingCopyBuildStepImplementation' => 'HarbormasterBuildStepImplementation',
+    'HarbormasterLeaseWorkingCopyFromBuildableBuildStepImplementation' => 'HarbormasterLeaseWorkingCopyBuildStepImplementation',
+    'HarbormasterLeaseWorkingCopyFromRepositoryBuildStepImplementation' => 'HarbormasterLeaseWorkingCopyBuildStepImplementation',
+    'HarbormasterLeaseWorkingCopyFromURLBuildStepImplementation' => 'HarbormasterLeaseWorkingCopyBuildStepImplementation',
     'HarbormasterLintMessagesController' => 'HarbormasterController',
     'HarbormasterLintPropertyView' => 'AphrontView',
     'HarbormasterManagePlansCapability' => 'PhabricatorPolicyCapability',
Index: src/applications/drydock/blueprint/DrydockWorkingCopyBlueprintImplementation.php
===================================================================
--- src/applications/drydock/blueprint/DrydockWorkingCopyBlueprintImplementation.php
+++ src/applications/drydock/blueprint/DrydockWorkingCopyBlueprintImplementation.php
@@ -23,11 +23,14 @@
     }
 
     $url = $lease->getAttribute('url');
+    $ref = $lease->getAttribute('ref');
     $buildable_phid = $lease->getAttribute('buildablePHID');
+    $repository_phid = $lease->getAttribute('repositoryPHID');
     
     if ($url) {
       $lease->setAttribute('resolved.target', 'url');
       $lease->setAttribute('resolved.repositoryURL', $url);
+      $lease->setAttribute('resolved.repositoryReference', $ref);
       $lease->save();
       
       $this->log(pht(
@@ -35,6 +38,20 @@
       $this->log(pht(
         'Resolved working copy repository URL as "%s"',
         $lease->getAttribute('resolved.repositoryURL')));
+    } else if ($repository_phid) {
+      $lease->setAttribute('resolved.target', 'commit');
+      $lease->setAttribute('resolved.repositoryPHID', $repository_phid);
+      $lease->setAttribute('resolved.commitIdentifier', $ref);
+      $lease->save();
+
+      $this->log(pht(
+        'Resolved working copy target as "commit"'));
+      $this->log(pht(
+        'Resolved working copy commit identifier as "%s"',
+        $lease->getAttribute('resolved.commitIdentifier')));
+      $this->log(pht(
+        'Resolved working copy repository PHID as "%s"',
+        $lease->getAttribute('resolved.repositoryPHID')));
     } else if ($buildable_phid) {
       $buildable = id(new HarbormasterBuildableQuery())
         ->setViewer(PhabricatorUser::getOmnipotentUser())
@@ -474,7 +491,18 @@
           $lease->getAttribute('resolved.commitIdentifier'));
         $this->log(pht('Checked out commit'));
       } else if ($lease->getAttribute('resolved.target') === 'url') {
-        // Leave as default; we use the working copy for cloning only.
+        if ($lease->getAttribute('resolved.repositoryReference') !== null) {
+          $this->log(pht(
+            'Checking out target reference "%s"',
+            $lease->getAttribute('resolved.repositoryReference')));
+          $cmd->execx(
+            'git checkout -f %s',
+            $lease->getAttribute('resolved.repositoryReference'));
+          $this->log(pht('Checked out reference'));
+        } else {
+          $this->log(pht(
+            'No target reference provided, leaving working directory as-is'));
+        }
       } else {
         throw new Exception(pht(
           'Target type %s not yet supported.',
@@ -513,13 +541,8 @@
       'Discovering initialized submodules in %s',
       $working_directory_path));
     list($stdout, $stderr) = $working_directory_cmd->execx('git config --local --list');
+    $matches = null;
     preg_match_all('/submodule\.(?<name>.*)\.url=(?<url>.*)/', $stdout, $matches);
-    $this->log(pht(
-      'Standard output is %s',
-      $stdout));
-    $this->log(pht(
-      'Submodule array is %s',
-      print_r($matches, true)));
     $submodules = array();
     for ($i = 0; $i < count($matches['name']); $i++) {
       $name = $matches['name'][$i];
Index: src/applications/harbormaster/customfield/HarbormasterCustomFieldRepository.php
===================================================================
--- /dev/null
+++ src/applications/harbormaster/customfield/HarbormasterCustomFieldRepository.php
@@ -0,0 +1,43 @@
+<?php
+
+final class HarbormasterCustomFieldRepository
+  extends PhabricatorStandardCustomFieldPHIDs {
+
+  public function getFieldType() {
+    return 'repository';
+  }
+
+  public function renderEditControl(array $handles) {
+    $value = $this->getFieldValue();
+
+    $control = id(new AphrontFormTokenizerControl())
+      ->setUser($this->getViewer())
+      ->setLabel($this->getFieldName())
+      ->setName($this->getFieldKey())
+      ->setDatasource(new DiffusionRepositoryDatasource())
+      ->setCaption($this->getCaption())
+      ->setValue(nonempty($value, array()));
+
+    $limit = $this->getFieldConfigValue('limit');
+    if ($limit) {
+      $control->setLimit($limit);
+    }
+
+    return $control;
+  }
+
+  public function appendToApplicationSearchForm(
+    PhabricatorApplicationSearchEngine $engine,
+    AphrontFormView $form,
+    $value) {
+
+    $control = id(new AphrontFormTokenizerControl())
+      ->setLabel($this->getFieldName())
+      ->setName($this->getFieldKey())
+      ->setDatasource(new DiffusionRepositoryDatasource())
+      ->setValue(nonempty($value, array()));
+
+    $form->appendControl($control);
+  }
+
+}
Index: src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyBuildStepImplementation.php
===================================================================
--- src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyBuildStepImplementation.php
+++ src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyBuildStepImplementation.php
@@ -1,17 +1,12 @@
 <?php
 
-final class HarbormasterLeaseWorkingCopyBuildStepImplementation
+abstract class HarbormasterLeaseWorkingCopyBuildStepImplementation
   extends HarbormasterBuildStepImplementation {
 
-  public function getName() {
-    return pht('Lease Working Copy');
-  }
-
-  public function getGenericDescription() {
-    return pht(
-      'Obtain a lease on a Drydock working copy of the '.
-      'current buildable for performing builds.');
-  }
+  abstract protected function getLeaseAttributes(
+    HarbormasterBuild $build,
+    HarbormasterBuildTarget $build_target,
+    array $settings);
 
   public function execute(
     HarbormasterBuild $build,
@@ -29,7 +24,8 @@
         array(
           'platform' => $settings['platform'],
           'buildablePHID' => $build->getBuildablePHID(),
-        ) + $custom_attributes)
+        ) + $this->getLeaseAttributes($build, $build_target, $settings)
+        + $custom_attributes)
       ->queueForActivation();
 
     // Create the associated artifact.
@@ -58,6 +54,8 @@
     );
   }
 
+  abstract protected function getLeaseFieldSpecifications();
+
   public function getFieldSpecifications() {
     return array(
       'name' => array(
@@ -70,6 +68,7 @@
         'type' => 'text',
         'required' => true,
       ),
+    ) + $this->getLeaseFieldSpecifications() + array(
       'attributes' => array(
         'name' => pht('Required Attributes'),
         'type' => 'textarea',
Index: src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromBuildableBuildStepImplementation.php
===================================================================
--- /dev/null
+++ src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromBuildableBuildStepImplementation.php
@@ -0,0 +1,30 @@
+<?php
+
+final class HarbormasterLeaseWorkingCopyFromBuildableBuildStepImplementation
+  extends HarbormasterLeaseWorkingCopyBuildStepImplementation {
+
+  public function getName() {
+    return pht('Lease Working Copy from Buildable');
+  }
+
+  public function getGenericDescription() {
+    return pht(
+      'Obtain a lease on a Drydock working copy of the '.
+      'current buildable for performing builds.');
+  }
+
+  protected function getLeaseAttributes(
+    HarbormasterBuild $build,
+    HarbormasterBuildTarget $build_target,
+    array $settings) {
+
+    return array(
+      'buildablePHID' => $build->getBuildablePHID(),
+    );
+  }
+
+  protected function getLeaseFieldSpecifications() {
+    return array();
+  }
+
+}
Index: src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromRepositoryBuildStepImplementation.php
===================================================================
--- /dev/null
+++ src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromRepositoryBuildStepImplementation.php
@@ -0,0 +1,44 @@
+<?php
+
+final class HarbormasterLeaseWorkingCopyFromRepositoryBuildStepImplementation
+  extends HarbormasterLeaseWorkingCopyBuildStepImplementation {
+
+  public function getName() {
+    return pht('Lease Working Copy from Repository');
+  }
+
+  public function getGenericDescription() {
+    return pht(
+      'Obtain a lease on a Drydock working copy of a '.
+      'repository hosted on Phabricator.');
+  }
+
+  protected function getLeaseAttributes(
+    HarbormasterBuild $build,
+    HarbormasterBuildTarget $build_target,
+    array $settings) {
+
+    return array(
+      'repositoryPHID' =>
+        head(phutil_json_decode(idx($settings, 'repositoryPHID'))),
+      'ref' => idx($settings, 'ref'),
+    );
+  }
+
+  protected function getLeaseFieldSpecifications() {
+    return array(
+      'repositoryPHID' => array(
+        'name' => pht('Repository'),
+        'type' => 'repository',
+        'required' => true,
+      ),
+      'ref' => array(
+        'name' => pht('Reference to Checkout'),
+        'type' => 'text',
+        'required' => true,
+        'caption' => pht('e.g. master'),
+      ),
+    );
+  }
+
+}
Index: src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromURLBuildStepImplementation.php
===================================================================
--- /dev/null
+++ src/applications/harbormaster/step/HarbormasterLeaseWorkingCopyFromURLBuildStepImplementation.php
@@ -0,0 +1,43 @@
+<?php
+
+final class HarbormasterLeaseWorkingCopyFromURLBuildStepImplementation
+  extends HarbormasterLeaseWorkingCopyBuildStepImplementation {
+
+  public function getName() {
+    return pht('Lease Working Copy from URL');
+  }
+
+  public function getGenericDescription() {
+    return pht(
+      'Obtain a lease on a Drydock working copy of a '.
+      'repository at a given URL.');
+  }
+
+  protected function getLeaseAttributes(
+    HarbormasterBuild $build,
+    HarbormasterBuildTarget $build_target,
+    array $settings) {
+
+    return array(
+      'url' => idx($settings, 'url'),
+      'ref' => idx($settings, 'ref'),
+    );
+  }
+
+  protected function getLeaseFieldSpecifications() {
+    return array(
+      'url' => array(
+        'name' => pht('Repository URL'),
+        'type' => 'text',
+        'required' => true,
+      ),
+      'ref' => array(
+        'name' => pht('Reference to Checkout'),
+        'type' => 'text',
+        'required' => true,
+        'caption' => pht('e.g. master'),
+      ),
+    );
+  }
+
+}