From 3ef22ab89b834d75c4fbcd255a96174f7492c3e2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gr=C3=A9goire=20Pineau?= <lyrixx@lyrixx.info>
Date: Mon, 7 Sep 2026 18:02:46 +0200
Subject: [PATCH] Support git's mnemonic diff prefixes in DiffParser

diff.mnemonicPrefix replaces the default "a/"/"b/" prefixes with
context-specific ones ("c/", "i/", "o/", "w/"), which DiffParser's
regexp didn't account for, causing a RuntimeException for tools like
GrumPHP that enable it.

Fixes #114
---
 src/Gitonomy/Git/Parser/DiffParser.php |  5 ++++-
 tests/Gitonomy/Git/Tests/DiffTest.php  | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/Gitonomy/Git/Parser/DiffParser.php b/src/Gitonomy/Git/Parser/DiffParser.php
index 3e95d1a..93de0a9 100644
--- a/src/Gitonomy/Git/Parser/DiffParser.php
+++ b/src/Gitonomy/Git/Parser/DiffParser.php
@@ -45,7 +45,10 @@ protected function doParse(): void
         $fileIndex = 0;
         while (!$this->isFinished()) {
             // 1. title
-            $vars = $this->consumeRegexp("/diff --git \"?(a\\/.*?)\"? \"?(b\\/.*?)\"?\n/");
+            // The prefix is normally "a" and "b", but git's diff.mnemonicPrefix option
+            // (used by tools such as GrumPHP) can produce other single-letter prefixes
+            // ("c"ommit, "i"ndex, "o"bject, "w"ork tree), or "1"/"2" with --no-index.
+            $vars = $this->consumeRegexp("/diff --git \"?([^\\/\\s]\\/.*?)\"? \"?([^\\/\\s]\\/.*?)\"?\n/");
             $oldName = $vars[1];
             $newName = $vars[2];
             // Get indexes from raw if it exists
diff --git a/tests/Gitonomy/Git/Tests/DiffTest.php b/tests/Gitonomy/Git/Tests/DiffTest.php
index a79fd4b..47624ac 100644
--- a/tests/Gitonomy/Git/Tests/DiffTest.php
+++ b/tests/Gitonomy/Git/Tests/DiffTest.php
@@ -224,6 +224,26 @@ public function testThrowErrorOnBlobGetWithoutIndex(): void
         $this->assertSame('', $file->getNewIndex());
     }
 
+    public function testMnemonicPrefix(): void
+    {
+        $this->expectUserDeprecationMessage('Using Diff::parse without raw information is deprecated. See https://github.com/gitonomy/gitlib/issues/227.');
+
+        // With `diff.mnemonicPrefix` enabled, git replaces the default "a/" and "b/"
+        // prefixes with context-specific ones, e.g. "c/" (commit) and "i/" (index)
+        // for `git diff --cached`. See https://github.com/gitonomy/gitlib/issues/114.
+        $diff = Diff::parse(<<<'DIFF'
+            diff --git c/composer.json i/composer.json
+            index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 100644
+            --- c/composer.json
+            +++ i/composer.json
+
+            DIFF);
+        $firstFile = $diff->getFiles()[0];
+
+        $this->assertSame('composer.json', $firstFile->getOldName());
+        $this->assertSame('composer.json', $firstFile->getNewName());
+    }
+
     public function testEmptyNewFile(): void
     {
         $this->expectUserDeprecationMessage('Using Diff::parse without raw information is deprecated. See https://github.com/gitonomy/gitlib/issues/227.');