From 2de3afdf68e78b8ed055baacf5005c4c02fa11b9 Mon Sep 17 00:00:00 2001
From: youdie006 <xncb135@korea.ac.kr>
Date: Tue, 8 Sep 2026 23:01:23 +0900
Subject: [PATCH] Quote the Index line like the other file-name headers

formatPatch runs the file name through quoteFileNameIfNeeded on every header
line it writes -- rename from/to, copy from/to, --- and +++ -- except Index:,
which got the raw name. A name needing quotes then produced a patch parsePatch
could not read back:

    createPatch('x\n--- evil', 'foo\n', 'bar\n')
    -> parsePatch throws: Missing "+++ ..." file header for evil

parsePatch gains the matching unquoteIfQuoted, the same inverse it already
applies to rename from/to.
---
 src/patch/create.ts  |  2 +-
 src/patch/parse.ts   |  3 ++-
 test/patch/create.js | 27 +++++++++++++++++++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/src/patch/create.ts b/src/patch/create.ts
index 52b5ed07..28cf292b 100644
--- a/src/patch/create.ts
+++ b/src/patch/create.ts
@@ -413,7 +413,7 @@ export function formatPatch(patch: StructuredPatch | StructuredPatch[], headerOp
     }
   } else {
     if (headerOptions.includeIndex && patch.oldFileName == patch.newFileName && patch.oldFileName !== undefined) {
-      ret.push('Index: ' + patch.oldFileName);
+      ret.push('Index: ' + quoteFileNameIfNeeded(patch.oldFileName));
     }
     if (headerOptions.includeUnderline) {
       ret.push('===================================================================');
diff --git a/src/patch/parse.ts b/src/patch/parse.ts
index d48f2d9a..16c1c625 100755
--- a/src/patch/parse.ts
+++ b/src/patch/parse.ts
@@ -196,7 +196,8 @@ export function parsePatch(uniDiff: string): StructuredPatch[] {
         //       -- ExplodingCabbage
         const headerMatch = (/^(?:Index:|diff(?: -r \w+)+)\s+/).exec(line);
         if (headerMatch) {
-          index.index = line.substring(headerMatch[0].length).trim();
+          // Inverse of the quoteFileNameIfNeeded applied to the `Index:` line by formatPatch
+          index.index = unquoteIfQuoted(line.substring(headerMatch[0].length).trim());
         }
       }
 
diff --git a/test/patch/create.js b/test/patch/create.js
index d9771678..ba07951b 100644
--- a/test/patch/create.js
+++ b/test/patch/create.js
@@ -704,6 +704,33 @@ describe('patch/create', function() {
         const diffResult = createTwoFilesPatch('testFileName', 'testFileName', 'foo\n', 'bar\n', undefined, undefined, {headerOptions: OMIT_HEADERS});
         expect(diffResult).to.equal(expectedResult);
       });
+
+      it('should quote the Index line for file names that require quoting, like the --- and +++ lines', function() {
+        const fileName = 'x\n--- evil';
+        const patch = createPatch(fileName, 'foo\n', 'bar\n');
+        expect(patch).to.equal(
+          'Index: "x\\n--- evil"\n'
+          + '===================================================================\n'
+          + '--- "x\\n--- evil"\n'
+          + '+++ "x\\n--- evil"\n'
+          + '@@ -1,1 +1,1 @@\n'
+          + '-foo\n'
+          + '+bar\n'
+        );
+        expect(parsePatch(patch)[0].oldFileName).to.equal(fileName);
+      });
+
+      it('should unquote a quoted Index line when parsing', function() {
+        const patch =
+          'Index: "x\\n--- evil"\n'
+          + '===================================================================\n'
+          + '--- "x\\n--- evil"\n'
+          + '+++ "x\\n--- evil"\n'
+          + '@@ -1,1 +1,1 @@\n'
+          + '-foo\n'
+          + '+bar\n';
+        expect(parsePatch(patch)[0].index).to.equal('x\n--- evil');
+      });
     });
 
     it('should respect maxEditLength', function() {