diff --git a/src/repository/api/ArcanistGitAPI.php b/src/repository/api/ArcanistGitAPI.php
--- a/src/repository/api/ArcanistGitAPI.php
+++ b/src/repository/api/ArcanistGitAPI.php
@@ -16,9 +16,6 @@
    */
   const GIT_MAGIC_ROOT_COMMIT = '4b825dc642cb6eb9a060e54bf8d69288fbee4904';
 
-  private $symbolicHeadCommit = 'HEAD';
-  private $resolvedHeadCommit;
-
   public static function newHookAPI($root) {
     return new ArcanistGitAPI($root);
   }
@@ -109,7 +106,7 @@
       // this as being the commits X and Y. If we log "B..Y", we only show
       // Y. With "Y --not B", we show X and Y.
 
-      $against = csprintf('%s --not %s', $this->getHeadCommit(), $this->getBaseCommit());
+      $against = csprintf('%s --not %s', 'HEAD', $this->getBaseCommit());
     }
 
     // NOTE: Windows escaping of "%" symbols apparently is inherently broken;
@@ -164,9 +161,8 @@
       }
 
       list($err, $merge_base) = $this->execManualLocal(
-        'merge-base %s %s',
-        $symbolic_commit,
-        $this->getHeadCommit());
+        'merge-base %s HEAD',
+        $symbolic_commit);
       if ($err) {
         throw new ArcanistUsageException(
           "Unable to find any git commit named '{$symbolic_commit}' in ".
@@ -174,7 +170,7 @@
       }
 
       $this->setBaseCommitExplanation(
-        "it is the merge-base of '{$symbolic_commit}' and {$this->symbolicHeadCommit}, as you ".
+        "it is the merge-base of '{$symbolic_commit}' and HEAD, as you ".
         "explicitly specified.");
       return trim($merge_base);
     }
@@ -305,43 +301,6 @@
     return trim($merge_base);
   }
 
-  public function getHeadCommit() {
-    if (!$this->supportsCommitRanges()) {
-      throw new ArcanistCapabilityNotSupportedException($this);
-    }
-
-    if ($this->resolvedHeadCommit === null) {
-      $this->resolvedHeadCommit =
-        $this->resolveCommit($this->symbolicHeadCommit);
-    }
-
-    return $this->resolvedHeadCommit;
-  }
-
-  final public function setHeadCommit($symbolic_commit) {
-    $this->symbolicHeadCommit = $symbolic_commit;
-    $this->reloadCommitRange();
-    return $this;
-  }
-
-  /** Translates a symbolic commit (HEAD^) to a commit identifier
-   * @param $symbolic_commit
-   * @return string the commit SHA
-   */
-  private function resolveCommit($symbolic_commit) {
-    list($err, $merge_base) = $this->execManualLocal(
-      'rev-parse %s',
-      $symbolic_commit);
-
-    if ($err) {
-      throw new ArcanistUsageException(
-        "Unable to find any git commit named '{$symbolic_commit}' in ".
-        "this repository.");
-    }
-
-    return trim($merge_base);
-  }
-
   private function getDiffFullOptions($detect_moves_and_renames = true) {
     $options = array(
       self::getDiffBaseOptions(),
@@ -376,8 +335,7 @@
   public function getFullGitDiff() {
     $options = $this->getDiffFullOptions();
     list($stdout) = $this->execxLocal(
-      "diff {$options} %s..%s --",
-      $this->getHeadCommit(),
+      "diff {$options} %s --",
       $this->getBaseCommit());
     return $stdout;
   }
@@ -443,9 +401,8 @@
     } else {
       // 2..N commits.
       list($stdout) = $this->execxLocal(
-        'log --first-parent --format=medium %s..%s',
-        $this->getBaseCommit(),
-        $this->getHeadCommit());
+        'log --first-parent --format=medium %s..HEAD',
+        $this->getBaseCommit());
     }
     return $stdout;
   }
diff --git a/src/repository/api/ArcanistRepositoryAPI.php b/src/repository/api/ArcanistRepositoryAPI.php
--- a/src/repository/api/ArcanistRepositoryAPI.php
+++ b/src/repository/api/ArcanistRepositoryAPI.php
@@ -575,10 +575,6 @@
     return $this;
   }
 
-  public function setHeadCommit($symbolic_commit) {
-    throw new ArcanistCapabilityNotSupportedException($this);
-  }
-
   final public function getBaseCommit() {
     if (!$this->supportsCommitRanges()) {
       throw new ArcanistCapabilityNotSupportedException($this);
@@ -592,10 +588,6 @@
     return $this->resolvedBaseCommit;
   }
 
-  public function getHeadCommit() {
-    throw new ArcanistCapabilityNotSupportedException($this);
-  }
-
   final public function reloadCommitRange() {
     $this->resolvedBaseCommit = null;
     $this->baseCommitExplanation = null;
diff --git a/src/workflow/ArcanistDiffWorkflow.php b/src/workflow/ArcanistDiffWorkflow.php
--- a/src/workflow/ArcanistDiffWorkflow.php
+++ b/src/workflow/ArcanistDiffWorkflow.php
@@ -395,11 +395,6 @@
         ),
       ),
       '*' => 'paths',
-      'range' => array(
-        'param' => 'range',
-        'help' => 'specify a commit range to include (BASE..HEAD)',
-        'supports' => array('git'),
-      )
     );
 
     if (phutil_is_windows()) {
@@ -438,20 +433,8 @@
         array_unshift($argv, '--ansi');
       }
 
-      $repo = $this->getRepositoryAPI();
-      $range = $this->getArgument('range', null);
-      $range_supported = $repo->supportsCommitRanges();
-      if ($range) {
-        if (!$range_supported) {
-          throw new Exception("ranged are not supported");
-        }
-
-        list($base, $head) = preg_split('(\\.\\.)', $range);
-        $repo->setHeadCommit($head);
-        $repo->setBaseCommit($base);
-
-      } else if ($range_supported) {
-        $repo->getBaseCommit();
+      if ($this->getRepositoryAPI()->supportsCommitRanges()) {
+        $this->getRepositoryAPI()->getBaseCommit();
       }
 
       $script = phutil_get_library_root('arcanist').'/../scripts/arcanist.php';
@@ -678,9 +661,7 @@
         if ($repository_api instanceof ArcanistSubversionAPI) {
           $repository_api->limitStatusToPaths($this->getArgument('paths'));
         }
-        if (!$this->getArgument('range')) {
-          $this->requireCleanWorkingCopy();
-        }
+        $this->requireCleanWorkingCopy();
       } catch (ArcanistUncommittedChangesException $ex) {
         if ($repository_api instanceof ArcanistMercurialAPI) {
           $use_dirty_changes = false;
@@ -1235,8 +1216,7 @@
   private function runLint() {
     if ($this->getArgument('nolint') ||
         $this->getArgument('only') ||
-        $this->isRawDiffSource() ||
-        $this->getArgument('range')) {
+        $this->isRawDiffSource()) {
       return ArcanistLintWorkflow::RESULT_SKIP;
     }
 
@@ -1317,8 +1297,7 @@
   private function runUnit() {
     if ($this->getArgument('nounit') ||
         $this->getArgument('only') ||
-        $this->isRawDiffSource() ||
-        $this->getArgument('range')) {
+        $this->isRawDiffSource()) {
       return ArcanistUnitWorkflow::RESULT_SKIP;
     }