git-format-patch - Online in the Cloud

PROGRAM:

NAME

git-format-patch - Prepare patches for e-mail submission

SYNOPSIS

git format-patch [-k] [(-o|--output-directory) <dir> | --stdout]
[--no-thread | --thread[=<style>]]
[(--attach|--inline)[=<boundary>] | --no-attach]
[-s | --signoff]
[--signature=<signature> | --no-signature]
[--signature-file=<file>]
[-n | --numbered | -N | --no-numbered]
[--start-number <n>] [--numbered-files]
[--in-reply-to=Message-Id] [--suffix=.<sfx>]
[--ignore-if-in-upstream]
[--subject-prefix=Subject-Prefix] [(--reroll-count|-v) <n>]
[--to=<email>] [--cc=<email>]
[--[no-]cover-letter] [--quiet] [--notes[=<ref>]]
[<common diff options>]
[ <since> | <revision range> ]

DESCRIPTION

Prepare each commit with its patch in one file per commit, formatted to resemble UNIX
mailbox format. The output of this command is convenient for e-mail submission or for use
with git am.

There are two ways to specify which commits to operate on.

1. A single commit, <since>, specifies that the commits leading to the tip of the current
branch that are not in the history that leads to the <since> to be output.

2. Generic <revision range> expression (see "SPECIFYING REVISIONS" section in
gitrevisions(7)) means the commits in the specified range.

The first rule takes precedence in the case of a single <commit>. To apply the second
rule, i.e., format everything since the beginning of history up until <commit>, use the
--root option: git format-patch --root <commit>. If you want to format only <commit>
itself, you can do this with git format-patch -1 <commit>.

By default, each output file is numbered sequentially from 1, and uses the first line of
the commit message (massaged for pathname safety) as the filename. With the
--numbered-files option, the output file names will only be numbers, without the first
line of the commit appended. The names of the output files are printed to standard output,
unless the --stdout option is specified.

If -o is specified, output files are created in <dir>. Otherwise they are created in the
current working directory.

By default, the subject of a single patch is "[PATCH] " followed by the concatenation of
lines from the commit message up to the first blank line (see the DISCUSSION section of
git-commit(1)).

When multiple patches are output, the subject prefix will instead be "[PATCH n/m] ". To
force 1/1 to be added for a single patch, use -n. To omit patch numbers from the subject,
use -N.

If given --thread, git-format-patch will generate In-Reply-To and References headers to
make the second and subsequent patch mails appear as replies to the first mail; this also
generates a Message-Id header to reference.

OPTIONS

-p, --no-stat
Generate plain patches without any diffstats.

-s, --no-patch
Suppress diff output. Useful for commands like git show that show the patch by
default, or to cancel the effect of --patch.

-U<n>, --unified=<n>
Generate diffs with <n> lines of context instead of the usual three.

--minimal
Spend extra time to make sure the smallest possible diff is produced.

--patience
Generate a diff using the "patience diff" algorithm.

--histogram
Generate a diff using the "histogram diff" algorithm.

--diff-algorithm={patience|minimal|histogram|myers}
Choose a diff algorithm. The variants are as follows:

default, myers
The basic greedy diff algorithm. Currently, this is the default.

minimal
Spend extra time to make sure the smallest possible diff is produced.

patience
Use "patience diff" algorithm when generating patches.

histogram
This algorithm extends the patience algorithm to "support low-occurrence common
elements".

For instance, if you configured diff.algorithm variable to a non-default value and
want to use the default one, then you have to use --diff-algorithm=default option.

--stat[=<width>[,<name-width>[,<count>]]]
Generate a diffstat. By default, as much space as necessary will be used for the
filename part, and the rest for the graph part. Maximum width defaults to terminal
width, or 80 columns if not connected to a terminal, and can be overridden by <width>.
The width of the filename part can be limited by giving another width <name-width>
after a comma. The width of the graph part can be limited by using
--stat-graph-width=<width> (affects all commands generating a stat graph) or by
setting diff.statGraphWidth=<width> (does not affect git format-patch). By giving a
third parameter <count>, you can limit the output to the first <count> lines, followed
by ... if there are more.

These parameters can also be set individually with --stat-width=<width>,
--stat-name-width=<name-width> and --stat-count=<count>.

--numstat
Similar to --stat, but shows number of added and deleted lines in decimal notation and
pathname without abbreviation, to make it more machine friendly. For binary files,
outputs two - instead of saying 0 0.

--shortstat
Output only the last line of the --stat format containing total number of modified
files, as well as number of added and deleted lines.

--dirstat[=<param1,param2,...>]
Output the distribution of relative amount of changes for each sub-directory. The
behavior of --dirstat can be customized by passing it a comma separated list of
parameters. The defaults are controlled by the diff.dirstat configuration variable
(see git-config(1)). The following parameters are available:

changes
Compute the dirstat numbers by counting the lines that have been removed from the
source, or added to the destination. This ignores the amount of pure code
movements within a file. In other words, rearranging lines in a file is not
counted as much as other changes. This is the default behavior when no parameter
is given.

lines
Compute the dirstat numbers by doing the regular line-based diff analysis, and
summing the removed/added line counts. (For binary files, count 64-byte chunks
instead, since binary files have no natural concept of lines). This is a more
expensive --dirstat behavior than the changes behavior, but it does count
rearranged lines within a file as much as other changes. The resulting output is
consistent with what you get from the other --*stat options.

files
Compute the dirstat numbers by counting the number of files changed. Each changed
file counts equally in the dirstat analysis. This is the computationally cheapest
--dirstat behavior, since it does not have to look at the file contents at all.

cumulative
Count changes in a child directory for the parent directory as well. Note that
when using cumulative, the sum of the percentages reported may exceed 100%. The
default (non-cumulative) behavior can be specified with the noncumulative
parameter.

<limit>
An integer parameter specifies a cut-off percent (3% by default). Directories
contributing less than this percentage of the changes are not shown in the output.

Example: The following will count changed files, while ignoring directories with less
than 10% of the total amount of changed files, and accumulating child directory counts
in the parent directories: --dirstat=files,10,cumulative.

--summary
Output a condensed summary of extended header information such as creations, renames
and mode changes.

--no-renames
Turn off rename detection, even when the configuration file gives the default to do
so.

--full-index
Instead of the first handful of characters, show the full pre- and post-image blob
object names on the "index" line when generating patch format output.

--binary
In addition to --full-index, output a binary diff that can be applied with git-apply.

--abbrev[=<n>]
Instead of showing the full 40-byte hexadecimal object name in diff-raw format output
and diff-tree header lines, show only a partial prefix. This is independent of the
--full-index option above, which controls the diff-patch output format. Non default
number of digits can be specified with --abbrev=<n>.

-B[<n>][/<m>], --break-rewrites[=[<n>][/<m>]]
Break complete rewrite changes into pairs of delete and create. This serves two
purposes:

It affects the way a change that amounts to a total rewrite of a file not as a series
of deletion and insertion mixed together with a very few lines that happen to match
textually as the context, but as a single deletion of everything old followed by a
single insertion of everything new, and the number m controls this aspect of the -B
option (defaults to 60%). -B/70% specifies that less than 30% of the original should
remain in the result for Git to consider it a total rewrite (i.e. otherwise the
resulting patch will be a series of deletion and insertion mixed together with context
lines).

When used with -M, a totally-rewritten file is also considered as the source of a
rename (usually -M only considers a file that disappeared as the source of a rename),
and the number n controls this aspect of the -B option (defaults to 50%). -B20%
specifies that a change with addition and deletion compared to 20% or more of the
file’s size are eligible for being picked up as a possible source of a rename to
another file.

-M[<n>], --find-renames[=<n>]
Detect renames. If n is specified, it is a threshold on the similarity index (i.e.
amount of addition/deletions compared to the file’s size). For example, -M90% means
Git should consider a delete/add pair to be a rename if more than 90% of the file
hasn’t changed. Without a % sign, the number is to be read as a fraction, with a
decimal point before it. I.e., -M5 becomes 0.5, and is thus the same as -M50%.
Similarly, -M05 is the same as -M5%. To limit detection to exact renames, use -M100%.
The default similarity index is 50%.

-C[<n>], --find-copies[=<n>]
Detect copies as well as renames. See also --find-copies-harder. If n is specified, it
has the same meaning as for -M<n>.

--find-copies-harder
For performance reasons, by default, -C option finds copies only if the original file
of the copy was modified in the same changeset. This flag makes the command inspect
unmodified files as candidates for the source of copy. This is a very expensive
operation for large projects, so use it with caution. Giving more than one -C option
has the same effect.

-D, --irreversible-delete
Omit the preimage for deletes, i.e. print only the header but not the diff between the
preimage and /dev/null. The resulting patch is not meant to be applied with patch or
git apply; this is solely for people who want to just concentrate on reviewing the
text after the change. In addition, the output obviously lack enough information to
apply such a patch in reverse, even manually, hence the name of the option.

When used together with -B, omit also the preimage in the deletion part of a
delete/create pair.

-l<num>
The -M and -C options require O(n^2) processing time where n is the number of
potential rename/copy targets. This option prevents rename/copy detection from running
if the number of rename/copy targets exceeds the specified number.

-O<orderfile>
Output the patch in the order specified in the <orderfile>, which has one shell glob
pattern per line. This overrides the diff.orderFile configuration variable (see git-
config(1)). To cancel diff.orderFile, use -O/dev/null.

-a, --text
Treat all files as text.

--ignore-space-at-eol
Ignore changes in whitespace at EOL.

-b, --ignore-space-change
Ignore changes in amount of whitespace. This ignores whitespace at line end, and
considers all other sequences of one or more whitespace characters to be equivalent.

-w, --ignore-all-space
Ignore whitespace when comparing lines. This ignores differences even if one line has
whitespace where the other line has none.

--ignore-blank-lines
Ignore changes whose lines are all blank.

--inter-hunk-context=<lines>
Show the context between diff hunks, up to the specified number of lines, thereby
fusing hunks that are close to each other.

-W, --function-context
Show whole surrounding functions of changes.

--ext-diff
Allow an external diff helper to be executed. If you set an external diff driver with
gitattributes(5), you need to use this option with git-log(1) and friends.

--no-ext-diff
Disallow external diff drivers.

--textconv, --no-textconv
Allow (or disallow) external text conversion filters to be run when comparing binary
files. See gitattributes(5) for details. Because textconv filters are typically a
one-way conversion, the resulting diff is suitable for human consumption, but cannot
be applied. For this reason, textconv filters are enabled by default only for git-
diff(1) and git-log(1), but not for git-format-patch(1) or diff plumbing commands.

--ignore-submodules[=<when>]
Ignore changes to submodules in the diff generation. <when> can be either "none",
"untracked", "dirty" or "all", which is the default. Using "none" will consider the
submodule modified when it either contains untracked or modified files or its HEAD
differs from the commit recorded in the superproject and can be used to override any
settings of the ignore option in git-config(1) or gitmodules(5). When "untracked" is
used submodules are not considered dirty when they only contain untracked content (but
they are still scanned for modified content). Using "dirty" ignores all changes to the
work tree of submodules, only changes to the commits stored in the superproject are
shown (this was the behavior until 1.7.0). Using "all" hides all changes to
submodules.

--src-prefix=<prefix>
Show the given source prefix instead of "a/".

--dst-prefix=<prefix>
Show the given destination prefix instead of "b/".

--no-prefix
Do not show any source or destination prefix.

For more detailed explanation on these common options, see also gitdiffcore(7).

-<n>
Prepare patches from the topmost <n> commits.

-o <dir>, --output-directory <dir>
Use <dir> to store the resulting files, instead of the current working directory.

-n, --numbered
Name output in [PATCH n/m] format, even with a single patch.

-N, --no-numbered
Name output in [PATCH] format.

--start-number <n>
Start numbering the patches at <n> instead of 1.

--numbered-files
Output file names will be a simple number sequence without the default first line of
the commit appended.

-k, --keep-subject
Do not strip/add [PATCH] from the first line of the commit log message.

-s, --signoff
Add Signed-off-by: line to the commit message, using the committer identity of
yourself. See the signoff option in git-commit(1) for more information.

--stdout
Print all commits to the standard output in mbox format, instead of creating a file
for each one.

--attach[=<boundary>]
Create multipart/mixed attachment, the first part of which is the commit message and
the patch itself in the second part, with Content-Disposition: attachment.

--no-attach
Disable the creation of an attachment, overriding the configuration setting.

--inline[=<boundary>]
Create multipart/mixed attachment, the first part of which is the commit message and
the patch itself in the second part, with Content-Disposition: inline.

--thread[=<style>], --no-thread
Controls addition of In-Reply-To and References headers to make the second and
subsequent mails appear as replies to the first. Also controls generation of the
Message-Id header to reference.

The optional <style> argument can be either shallow or deep. shallow threading makes
every mail a reply to the head of the series, where the head is chosen from the cover
letter, the --in-reply-to, and the first patch mail, in this order. deep threading
makes every mail a reply to the previous one.

The default is --no-thread, unless the format.thread configuration is set. If --thread
is specified without a style, it defaults to the style specified by format.thread if
any, or else shallow.

Beware that the default for git send-email is to thread emails itself. If you want git
format-patch to take care of threading, you will want to ensure that threading is
disabled for git send-email.

--in-reply-to=Message-Id
Make the first mail (or all the mails with --no-thread) appear as a reply to the given
Message-Id, which avoids breaking threads to provide a new patch series.

--ignore-if-in-upstream
Do not include a patch that matches a commit in <until>..<since>. This will examine
all patches reachable from <since> but not from <until> and compare them with the
patches being generated, and any patch that matches is ignored.

--subject-prefix=<Subject-Prefix>
Instead of the standard [PATCH] prefix in the subject line, instead use
[<Subject-Prefix>]. This allows for useful naming of a patch series, and can be
combined with the --numbered option.

-v <n>, --reroll-count=<n>
Mark the series as the <n>-th iteration of the topic. The output filenames have v<n>
prepended to them, and the subject prefix ("PATCH" by default, but configurable via
the --subject-prefix option) has ` v<n>` appended to it. E.g. --reroll-count=4 may
produce v4-0001-add-makefile.patch file that has "Subject: [PATCH v4 1/20] Add
makefile" in it.

--to=<email>
Add a To: header to the email headers. This is in addition to any configured headers,
and may be used multiple times. The negated form --no-to discards all To: headers
added so far (from config or command line).

--cc=<email>
Add a Cc: header to the email headers. This is in addition to any configured headers,
and may be used multiple times. The negated form --no-cc discards all Cc: headers
added so far (from config or command line).

--from, --from=<ident>
Use ident in the From: header of each commit email. If the author ident of the commit
is not textually identical to the provided ident, place a From: header in the body of
the message with the original author. If no ident is given, use the committer ident.

Note that this option is only useful if you are actually sending the emails and want
to identify yourself as the sender, but retain the original author (and git am will
correctly pick up the in-body header). Note also that git send-email already handles
this transformation for you, and this option should not be used if you are feeding the
result to git send-email.

--add-header=<header>
Add an arbitrary header to the email headers. This is in addition to any configured
headers, and may be used multiple times. For example, --add-header="Organization:
git-foo". The negated form --no-add-header discards all (To:, Cc:, and custom) headers
added so far from config or command line.

--[no-]cover-letter
In addition to the patches, generate a cover letter file containing the branch
description, shortlog and the overall diffstat. You can fill in a description in the
file before sending it out.

--notes[=<ref>]
Append the notes (see git-notes(1)) for the commit after the three-dash line.

The expected use case of this is to write supporting explanation for the commit that
does not belong to the commit log message proper, and include it with the patch
submission. While one can simply write these explanations after format-patch has run
but before sending, keeping them as Git notes allows them to be maintained between
versions of the patch series (but see the discussion of the notes.rewrite
configuration options in git-notes(1) to use this workflow).

--[no]-signature=<signature>
Add a signature to each message produced. Per RFC 3676 the signature is separated from
the body by a line with '-- ' on it. If the signature option is omitted the signature
defaults to the Git version number.

--signature-file=<file>
Works just like --signature except the signature is read from a file.

--suffix=.<sfx>
Instead of using .patch as the suffix for generated filenames, use specified suffix. A
common alternative is --suffix=.txt. Leaving this empty will remove the .patch suffix.

Note that the leading character does not have to be a dot; for example, you can use
--suffix=-patch to get 0001-description-of-my-change-patch.

-q, --quiet
Do not print the names of the generated files to standard output.

--no-binary
Do not output contents of changes in binary files, instead display a notice that those
files changed. Patches generated using this option cannot be applied properly, but
they are still useful for code review.

--zero-commit
Output an all-zero hash in each patch’s From header instead of the hash of the commit.

--root
Treat the revision argument as a <revision range>, even if it is just a single commit
(that would normally be treated as a <since>). Note that root commits included in the
specified range are always formatted as creation patches, independently of this flag.

CONFIGURATION

You can specify extra mail header lines to be added to each message, defaults for the
subject prefix and file suffix, number patches when outputting more than one patch, add
"To" or "Cc:" headers, configure attachments, and sign off patches with configuration
variables.

[format]
headers = "Organization: git-foo\n"
subjectPrefix = CHANGE
suffix = .txt
numbered = auto
to = <email>
cc = <email>
attach [ = mime-boundary-string ]
signOff = true
coverletter = auto

DISCUSSION

The patch produced by git format-patch is in UNIX mailbox format, with a fixed "magic"
time stamp to indicate that the file is output from format-patch rather than a real
mailbox, like so:

From 8f72bad1baf19a53459661343e21d6491c3908d3 Mon Sep 17 00:00:00 2001
From: Tony Luck <[email protected]>
Date: Tue, 13 Jul 2010 11:42:54 -0700
Subject: [PATCH] =?UTF-8?q?[IA64]=20Put=20ia64=20config=20files=20on=20the=20?=
=?UTF-8?q?Uwe=20Kleine-K=C3=B6nig=20diet?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

arch/arm config files were slimmed down using a python script
(See commit c2330e286f68f1c408b4aa6515ba49d57f05beae comment)

Do the same for ia64 so we can have sleek & trim looking
...

Typically it will be placed in a MUA’s drafts folder, edited to add timely commentary that
should not go in the changelog after the three dashes, and then sent as a message whose
body, in our example, starts with "arch/arm config files were...". On the receiving end,
readers can save interesting patches in a UNIX mailbox and apply them with git-am(1).

When a patch is part of an ongoing discussion, the patch generated by git format-patch can
be tweaked to take advantage of the git am --scissors feature. After your response to the
discussion comes a line that consists solely of "-- >8 --" (scissors and perforation),
followed by the patch with unnecessary header fields removed:

...
> So we should do such-and-such.

Makes sense to me. How about this patch?

-- >8 --
Subject: [IA64] Put ia64 config files on the Uwe Kleine-König diet

arch/arm config files were slimmed down using a python script
...

When sending a patch this way, most often you are sending your own patch, so in addition
to the "From $SHA1 $magic_timestamp" marker you should omit From: and Date: lines from the
patch file. The patch title is likely to be different from the subject of the discussion
the patch is in response to, so it is likely that you would want to keep the Subject:
line, like the example above.

Checking for patch corruption
Many mailers if not set up properly will corrupt whitespace. Here are two common types of
corruption:

· Empty context lines that do not have any whitespace.

· Non-empty context lines that have one extra whitespace at the beginning.

One way to test if your MUA is set up correctly is:

· Send the patch to yourself, exactly the way you would, except with To: and Cc: lines
that do not contain the list and maintainer address.

· Save that patch to a file in UNIX mailbox format. Call it a.patch, say.

· Apply it:

$ git fetch <project> master:test-apply
$ git checkout test-apply
$ git reset --hard
$ git am a.patch

If it does not apply correctly, there can be various reasons.

· The patch itself does not apply cleanly. That is bad but does not have much to do with
your MUA. You might want to rebase the patch with git-rebase(1) before regenerating it
in this case.

· The MUA corrupted your patch; "am" would complain that the patch does not apply. Look
in the .git/rebase-apply/ subdirectory and see what patch file contains and check for
the common corruption patterns mentioned above.

· While at it, check the info and final-commit files as well. If what is in final-commit
is not exactly what you would want to see in the commit log message, it is very likely
that the receiver would end up hand editing the log message when applying your patch.
Things like "Hi, this is my first patch.\n" in the patch e-mail should come after the
three-dash line that signals the end of the commit message.

MUA-SPECIFIC HINTS

Here are some hints on how to successfully submit patches inline using various mailers.

GMail
GMail does not have any way to turn off line wrapping in the web interface, so it will
mangle any emails that you send. You can however use "git send-email" and send your
patches through the GMail SMTP server, or use any IMAP email client to connect to the
google IMAP server and forward the emails through that.

For hints on using git send-email to send your patches through the GMail SMTP server, see
the EXAMPLE section of git-send-email(1).

For hints on submission using the IMAP interface, see the EXAMPLE section of git-imap-
send(1).

Thunderbird
By default, Thunderbird will both wrap emails as well as flag them as being format=flowed,
both of which will make the resulting email unusable by Git.

There are three different approaches: use an add-on to turn off line wraps, configure
Thunderbird to not mangle patches, or use an external editor to keep Thunderbird from
mangling the patches.

Approach #1 (add-on)
Install the Toggle Word Wrap add-on that is available from
https://addons.mozilla.org/thunderbird/addon/toggle-word-wrap/ It adds a menu entry
"Enable Word Wrap" in the composer’s "Options" menu that you can tick off. Now you can
compose the message as you otherwise do (cut + paste, git format-patch | git
imap-send, etc), but you have to insert line breaks manually in any text that you
type.

Approach #2 (configuration)
Three steps:

1. Configure your mail server composition as plain text: Edit...Account
Settings...Composition & Addressing, uncheck "Compose Messages in HTML".

2. Configure your general composition window to not wrap.

In Thunderbird 2: Edit..Preferences..Composition, wrap plain text messages at 0

In Thunderbird 3: Edit..Preferences..Advanced..Config Editor. Search for
"mail.wrap_long_lines". Toggle it to make sure it is set to false. Also, search
for "mailnews.wraplength" and set the value to 0.

3. Disable the use of format=flowed: Edit..Preferences..Advanced..Config Editor.
Search for "mailnews.send_plaintext_flowed". Toggle it to make sure it is set to
false.

After that is done, you should be able to compose email as you otherwise would (cut +
paste, git format-patch | git imap-send, etc), and the patches will not be mangled.

Approach #3 (external editor)
The following Thunderbird extensions are needed: AboutConfig from
http://aboutconfig.mozdev.org/ and External Editor from
http://globs.org/articles.php?lng=en&pg=8

1. Prepare the patch as a text file using your method of choice.

2. Before opening a compose window, use Edit→Account Settings to uncheck the "Compose
messages in HTML format" setting in the "Composition & Addressing" panel of the
account to be used to send the patch.

3. In the main Thunderbird window, before you open the compose window for the patch,
use Tools→about:config to set the following to the indicated values:

mailnews.send_plaintext_flowed => false
mailnews.wraplength => 0

4. Open a compose window and click the external editor icon.

5. In the external editor window, read in the patch file and exit the editor
normally.

Side note: it may be possible to do step 2 with about:config and the following
settings but no one’s tried yet.

mail.html_compose => false
mail.identity.default.compose_html => false
mail.identity.id?.compose_html => false

There is a script in contrib/thunderbird-patch-inline which can help you include
patches with Thunderbird in an easy way. To use it, do the steps above and then use
the script as the external editor.

KMail
This should help you to submit patches inline using KMail.

1. Prepare the patch as a text file.

2. Click on New Mail.

3. Go under "Options" in the Composer window and be sure that "Word wrap" is not set.

4. Use Message → Insert file... and insert the patch.

5. Back in the compose window: add whatever other text you wish to the message, complete
the addressing and subject fields, and press send.

EXAMPLES

· Extract commits between revisions R1 and R2, and apply them on top of the current
branch using git am to cherry-pick them:

$ git format-patch -k --stdout R1..R2 | git am -3 -k

· Extract all commits which are in the current branch but not in the origin branch:

$ git format-patch origin

For each commit a separate file is created in the current directory.

· Extract all commits that lead to origin since the inception of the project:

$ git format-patch --root origin

· The same as the previous one:

$ git format-patch -M -B origin

Additionally, it detects and handles renames and complete rewrites intelligently to
produce a renaming patch. A renaming patch reduces the amount of text output, and
generally makes it easier to review. Note that non-Git "patch" programs won’t
understand renaming patches, so use it only when you know the recipient uses Git to
apply your patch.

· Extract three topmost commits from the current branch and format them as e-mailable
patches:

$ git format-patch -3

Use git-format-patch online using onworks.net services