From cf00c44cc3b6bd2b41fcf31a4283fceb312c8f90 Mon Sep 17 00:00:00 2001
From: epriestley <git@epriestley.com>
Date: Thu, 22 Dec 2011 13:48:17 -0800
Subject: [PATCH] Decompose TYPE_MULTICOPY changes into a MOVE_HERE plus one or
 more COPY_HERE

Summary:
See T419 for some philosophical musing on this. The "ideal" way to represent
these changes is two or more COPY_HERE plus a DELETE, but we can't build the
DELETE patch yet.

Just turn one of the COPY_HERE changes into a MOVE_HERE. While less idealistic,
I think this should always work.

Test Plan: This seemed to cleanly apply TenXer D265. TenXer guys, can you
confirm that this makes it actually patch correctly?

Reviewers: jonathanhester, bizrad6, kdeggelman, jungejason, btrahan

Reviewed By: jungejason

CC: aran, jonathanhester, jungejason, epriestley

Maniphest Tasks: T419

Differential Revision: https://secure.phabricator.com/D1270
---
 src/parser/bundle/ArcanistBundle.php | 44 ++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/src/parser/bundle/ArcanistBundle.php b/src/parser/bundle/ArcanistBundle.php
index c9f7b3f6..21db9bf1 100644
--- a/src/parser/bundle/ArcanistBundle.php
+++ b/src/parser/bundle/ArcanistBundle.php
@@ -207,6 +207,50 @@ class ArcanistBundle {
   public function toGitPatch() {
     $result = array();
     $changes = $this->getChanges();
+
+    foreach (array_keys($changes) as $multicopy_key) {
+      $multicopy_change = $changes[$multicopy_key];
+
+      $type = $multicopy_change->getType();
+      if ($type != ArcanistDiffChangeType::TYPE_MULTICOPY) {
+        continue;
+      }
+
+      // Decompose MULTICOPY into one MOVE_HERE and several COPY_HERE because
+      // we need more information than we have in order to build a delete patch
+      // and represent it as a bunch of COPY_HERE plus a delete. For details,
+      // see T419.
+
+      // Basically, MULTICOPY means there are 2 or more corresponding COPY_HERE
+      // changes, so find one of them arbitrariy and turn it into a MOVE_HERE.
+
+      // TODO: We might be able to do this more cleanly after T230 is resolved.
+
+      $decompose_okay = false;
+      foreach ($changes as $change_key => $change) {
+        if ($change->getType() != ArcanistDiffChangeType::TYPE_COPY_HERE) {
+          continue;
+        }
+        if ($change->getOldPath() != $multicopy_change->getCurrentPath()) {
+          continue;
+        }
+        $decompose_okay = true;
+        $change = clone $change;
+        $change->setType(ArcanistDiffChangeType::TYPE_MOVE_HERE);
+        $changes[$change_key] = $change;
+
+        // The multicopy is now fully represented by MOVE_HERE plus one or more
+        // COPY_HERE, so throw it away.
+        unset($changes[$multicopy_key]);
+        break;
+      }
+
+      if (!$decompose_okay) {
+        throw new Exception(
+          "Failed to decompose multicopy changeset in order to generate diff.");
+      }
+    }
+
     foreach ($changes as $change) {
       $type = $change->getType();
       $file_type = $change->getFileType();