Support git-format-patch format in diff parser

Summary:
Fixes T4063. The `git format-patch` command produces a special header
and footer which we need to detect, strip, and parse.

Test Plan:
  - Added and ran unit tests.
  - Submitted a diff with `git format-patch HEAD^ --stdout | arc diff --raw`.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4063

Differential Revision: https://secure.phabricator.com/D8547

src/parser/ArcanistDiffParser.php

@@ -193,6 +193,22 @@ final class ArcanistDiffParser {
       throw new Exception("Can't parse an empty diff!");
     }
 
+    // Detect `git-format-patch`, by looking for a "---" line somewhere in
+    // the file and then a footer with Git version number, which looks like
+    // this:
+    //
+    //   --
+    //   1.8.4.2
+    //
+    // Note that `git-format-patch` adds a space after the "--", but we don't
+    // require it when detecting patches, as trailing whitespace can easily be
+    // lost in transit.
+    $detect_patch = '/^---$.*^-- ?[\s\d.]+\z/ms';
+    $message = null;
+    if (preg_match($detect_patch, $diff)) {
+      list($message, $diff) = $this->stripGitFormatPatch($diff);
+    }
+
     $this->didStartParse($diff);
 
     // Strip off header comments. While `patch` allows comments anywhere in the
@@ -203,6 +219,14 @@ final class ArcanistDiffParser {
       $line = $this->nextLine();
     }
 
+    if (strlen($message)) {
+      // If we found a message during pre-parse steps, add it to the resulting
+      // changes here.
+      $change = $this->buildChange(null)
+        ->setType(ArcanistDiffChangeType::TYPE_MESSAGE)
+        ->setMetadata('message', $message);
+    }
+
     do {
       $patterns = array(
         // This is a normal SVN text change, probably from "svn diff".
@@ -1346,4 +1370,42 @@ final class ArcanistDiffParser {
     return array($old, $new);
   }
 
+
+  /**
+   * Strip the header and footer off a `git-format-patch` diff.
+   *
+   * Returns a parseable normal diff and a textual commit message.
+   */
+  private function stripGitFormatPatch($diff) {
+
+    // We can parse this by splitting it into two pieces over and over again
+    // along different section dividers:
+    //
+    //   1. Mail headers.
+    //   2. ("\n\n")
+    //   3. Mail body.
+    //   4. ("---")
+    //   5. Diff stat section.
+    //   6. ("\n\n")
+    //   7. Actual diff body.
+    //   8. ("--")
+    //   9. Patch footer.
+
+    list($head, $tail) = preg_split("/^---$/m", $diff, 2);
+    list($mail_headers, $mail_body) = explode("\n\n", $head, 2);
+    list($body, $foot) = preg_split('/^-- ?$/m', $tail, 2);
+    list($stat, $diff) = explode("\n\n", $body, 2);
+
+    // Rebuild the commit message by putting the subject line back on top of it,
+    // if we can find one.
+    $matches = null;
+    $pattern = '/^Subject: (?:\[PATCH\] )?(.*)$/mi';
+    if (preg_match($pattern, $mail_headers, $matches)) {
+      $mail_body = $matches[1]."\n\n".$mail_body;
+      $mail_body = rtrim($mail_body);
+    }
+
+    return array($mail_body, $diff);
+  }
+
 }

src/parser/__tests__/ArcanistDiffParserTestCase.php

@@ -575,6 +575,20 @@ EOTEXT
       case 'svnlook-delete.svndiff':
         $this->assertEqual(1, count($changes));
         break;
+      case 'git-format-patch.gitdiff':
+        $this->assertEqual(2, count($changes));
+
+        $change = array_shift($changes);
+        $this->assertEqual(
+          ArcanistDiffChangeType::TYPE_MESSAGE,
+          $change->getType());
+        $this->assertEqual("WIP", $change->getMetadata('message'));
+
+        $change = array_shift($changes);
+        $this->assertEqual(
+          ArcanistDiffChangeType::TYPE_CHANGE,
+          $change->getType());
+        break;
       default:
         throw new Exception("No test block for diff file {$diff_file}.");
         break;

src/parser/__tests__/diff/git-format-patch.gitdiff

@@ -0,0 +1,21 @@
+From 9c68ca45aafefc1f9b9f49a7b380d6159d3e93c1 Mon Sep 17 00:00:00 2001
+From: epriestley <git@epriestley.com>
+Date: Sat, 15 Mar 2014 08:54:34 -0700
+Subject: [PATCH] WIP
+
+---
+ number_j.txt | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/number_j.txt b/number_j.txt
+index bd44aa2..d64876d 100644
+--- a/number_j.txt
++++ b/number_j.txt
+@@ -138,3 +138,4 @@ j
+ j
+ j
+ j
++j
+--
+1.8.4.2
+

src/workflow/ArcanistDiffWorkflow.php

@@ -1574,6 +1574,7 @@ EOTEXT
           ));
       }
     }
+
     $old_message = $template;
 
     $included = array();