Working with git format-patch Output

Applying git format-patch Patches

git format-patch generates patches in an email-like format that includes commit metadata. The Diff Patch Applier can process the diff portion of these patches.

format-patch Output Structure

From abc123 Mon Sep 17 00:00:00 2001
From: Author Name <author@example.com>
Date: Mon, 1 Jan 2024 12:00:00 +0000
Subject: [PATCH] Fix null pointer in user handler

Description of the change...
---
 src/handler.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/handler.js b/src/handler.js
index abc1234..def5678 100644
--- a/src/handler.js
+++ b/src/handler.js
@@ -10,7 +10,8 @@
 function handleUser(req, res) {
-  const user = getUser(req.params.id);
-  res.json(user.profile);
+  const user = getUser(req.params.id);
+  if (!user) return res.status(404).json({ error: "Not found" });
+  res.json(user.profile);
 }

Extracting the Diff

The Diff Patch Applier's parser is designed to skip non-diff content and find the ---/+++ headers and @@ hunk headers. You can paste the entire format-patch output, and it will extract the diff portion automatically.

Multiple Commits

If you have a patch series (multiple commits), each will have its own diff --git section. The tool processes all diff sections it finds, applying hunks from each in order.

Stat Line

The summary line (1 file changed, 3 insertions(+), 2 deletions(-)) is informational and ignored by the parser. Only the actual diff lines affect the patch application.

Common Issues

• Binary patches — git format-patch can include binary diffs that this tool cannot process. These appear as Binary files differ
• Rename detection — renamed files show as rename from/to which the parser skips
• Mode changes — old mode/new mode lines are informational and ignored