format-patch Git Command Guide

The git format-patch command is used to prepare each commit with its patch in a message format suitable for email submission. It formats commits as UNIX mailbox messages with metadata headers, commit messages, and unified diffs for use with git am.

git format-patch Syntax:

git format-patch [-k] [(-o|--output-directory) <dir> | --stdout]
                 [--no-thread | --thread[=<style>]]
                 [-s | --signoff] [-n | --numbered | -N | --no-numbered]
                 [--start-number <n>] [--in-reply-to=<message-id>]
                 [--subject-prefix=<prefix>] [--rfc[=<rfc>]]
                 [--to=<email>] [--cc=<email>] [--[no-]cover-letter]
                 [--range-diff=<previous>] [<common-diff-options>]
                 [ <since> | <revision-range> ]

Options:

Option	Description
-o , —output-directory	Output to specified directory
—stdout	Output to standard output
-s, —signoff	Add signoff line
-n, —numbered	Use [PATCH n/m] subject prefix
-N, —no-numbered	Don’t use patch numbers in subject
—start-number	Start numbering patches at
—cover-letter	Generate cover letter
—no-cover-letter	Don’t generate cover letter
—subject-prefix=	Custom subject prefix
—rfc[=]	Use RFC prefix for subject
—range-diff=	Add range diff to cover letter
—to=	Add To: header
—cc=	Add Cc: header
—in-reply-to=	Set In-Reply-To header
—thread[=	Add threading headers
-k	Don’t strip/comment patches
—suffix=.	Use different suffix (default .patch)

Parameters:

Parameter	Description
[	]

git format-patch Command Samples:

Format last 3 commits

git format-patch -3

Create patch files for the last 3 commits in current branch.

Format from specific commit

git format-patch HEAD~5

Format all commits from HEAD~5 to HEAD.

Output to specific directory

git format-patch -o ~/patches HEAD~10

Create patches in ~/patches directory for last 10 commits.

Format as RFC patch

git format-patch --rfc HEAD~3

Create RFC-style patches with [RFC PATCH] subject prefix.

Include cover letter

git format-patch --cover-letter HEAD~5

Create patches with a cover letter for the series.

Format with range diff

git format-patch --range-diff=main HEAD~3

Include range diff in cover letter showing revisions.

Output to stdout

git format-patch --stdout HEAD~1 > feature.patch

Output single patch to stdout (redirected to file).

Add email headers

git format-patch --to=johndoe@example.com --cc=team@example.com HEAD~5

Create patches with To: and Cc: headers for direct mailing.

Custom numbering

git format-patch --start-number=100 HEAD~10

Start patch numbering from 100 instead of 1.

Format to current directory

git format-patch . HEAD~20..HEAD

Format patches in current directory for specified range.

How do I create patches for email submission?

To create patches for email, run:

git format-patch <since>

This creates numbered patch files for each commit.

How can I include a cover letter?

To include a cover letter with your patch series, use:

git format-patch --cover-letter HEAD~5

This creates 0000-cover-letter.patch with series overview.

How do I change the output directory?

To specify output directory, use -o:

git format-patch -o ~/patches HEAD~10

How do I create RFC patches?

To create RFC-style patches, use —rfc:

git format-patch --rfc HEAD~3

This uses [RFC PATCH] instead of [PATCH] in subjects.

How can I preview patch output?

To preview what format-patch will create, use:

git format-patch --stdout HEAD~1 | head -50

How do I control patch numbering?

To start numbering from a specific number, use:

git format-patch --start-number=10 HEAD~5

How do I add range diff to cover letter?

To include range diff showing revisions, use:

git format-patch --range-diff=main --cover-letter HEAD~3

How do I format patches for mailing lists?

To prepare patches for mailing list submission, use:

git format-patch --thread --to=maintainer@example.com HEAD~5

This adds proper threading headers for mailing list.

How do I test patches before sending?

To test patches before distribution, use:

git am --dry-run < patch-file

This checks what git am would do without actually applying.

How do I handle large patch sets?

For large patch sets, consider using:

git format-patch --cover-letter --range-diff=v1.0 HEAD~50

This creates well-documented series with overview and revision diffs.

Applications of the git format-patch command

Preparing patches for code review via email
Contributing to projects that accept patch emails
Creating backup of work for offline development
Generating patch series for maintainer review
Preparing patches for kernel and open source project submissions
Creating reproducible patch archives for distribution