From f9f2092246d26362aae06e7e534db906d4c1ca4f Mon Sep 17 00:00:00 2001
From: epriestley <git@epriestley.com>
Date: Fri, 11 Jul 2014 10:45:11 -0700
Subject: [PATCH] Use `git diff a b` for ranges, not `git diff a..b`

Summary:
These are documented as being identical, but `git diff a b` works if `a` is a tree (for example, `4b825d...`, the empty tree hash), but `git diff a..b` does not.

Particularly, with the `a..b` form, `arc diff --base arc:empty` does not work. With the `a b` form, it does.

Test Plan: Ran `arc diff --base arc:empty` in a repository and got a diff.

Reviewers: btrahan, talshiri

Reviewed By: talshiri

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9898
---
 src/repository/api/ArcanistGitAPI.php | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/repository/api/ArcanistGitAPI.php b/src/repository/api/ArcanistGitAPI.php
index e9f05f58..514f6068 100644
--- a/src/repository/api/ArcanistGitAPI.php
+++ b/src/repository/api/ArcanistGitAPI.php
@@ -429,17 +429,20 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
    * @param head revision. If this is null, the generated diff will include the
    * working copy
    */
-  public function getFullGitDiff($base, $head=null) {
+  public function getFullGitDiff($base, $head = null) {
     $options = $this->getDiffFullOptions();
 
-    $diff_revision = $base;
-    if ($head) {
-      $diff_revision .= '..'.$head;
+    if ($head !== null) {
+      list($stdout) = $this->execxLocal(
+        "diff {$options} %s %s --",
+        $base,
+        $head);
+    } else {
+      list($stdout) = $this->execxLocal(
+        "diff {$options} %s --",
+        $base);
     }
 
-    list($stdout) = $this->execxLocal(
-      "diff {$options} %s --",
-      $diff_revision);
     return $stdout;
   }