man1/git-patch-id.1

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.\"     Title: git-patch-id
.\"    Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author]
.\" Generator: DocBook XSL Stylesheets v1.79.2 <http://docbook.sf.net/>
.\"      Date: 2025-11-16
.\"    Manual: Git Manual
.\"    Source: Git 2.52.0.rc2.22.gc93f1a0fa3
.\"  Language: English
.\"
.TH "GIT\-PATCH\-ID" "1" "2025-11-16" "Git 2\&.52\&.0\&.rc2\&.22\&.gc" "Git Manual"
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.SH "NAME"
git-patch-id \- Compute unique ID for a patch
.SH "SYNOPSIS"
.sp
.nf
\fBgit\fR \fBpatch\-id\fR [\fB\-\-stable\fR | \fB\-\-unstable\fR | \fB\-\-verbatim\fR]
.fi
.SH "DESCRIPTION"
.sp
Read a patch from the standard input and compute the patch ID for it\&.
.sp
A "patch ID" is nothing but a sum of SHA\-1 of the file diffs associated with a patch, with line numbers ignored\&. As such, it\(cqs "reasonably stable", but at the same time also reasonably unique, i\&.e\&., two patches that have the same "patch ID" are almost guaranteed to be the same thing\&.
.sp
The main usecase for this command is to look for likely duplicate commits\&.
.sp
When dealing with \fBgit\fR \fBdiff\-tree\fR output, it takes advantage of the fact that the patch is prefixed with the object name of the commit, and outputs two 40\-byte hexadecimal strings\&. The first string is the patch ID, and the second string is the commit ID\&. This can be used to make a mapping from patch ID to commit ID\&.
.SH "OPTIONS"
.PP
\fB\-\-verbatim\fR
.RS 4
Calculate the patch\-id of the input as it is given, do not strip any whitespace\&.
.sp
This is the default if
\fBpatchid\&.verbatim\fR
is
\fBtrue\fR\&.
.RE
.PP
\fB\-\-stable\fR
.RS 4
Use a "stable" sum of hashes as the patch ID\&. With this option:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Reordering file diffs that make up a patch does not affect the ID\&. In particular, two patches produced by comparing the same two trees with two different settings for
\fB\-O\fR\fI<orderfile>\fR
result in the same patch ID signature, thereby allowing the computed result to be used as a key to index some meta\-information about the change between the two trees;
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Result is different from the value produced by git 1\&.9 and older or produced when an "unstable" hash (see
\fB\-\-unstable\fR
below) is configured \- even when used on a diff output taken without any use of
\fB\-O\fR\fI<orderfile>\fR, thereby making existing databases storing such "unstable" or historical patch\-ids unusable\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
All whitespace within the patch is ignored and does not affect the id\&.
.RE
.sp
This is the default if
\fBpatchid\&.stable\fR
is set to
\fBtrue\fR\&.
.RE
.PP
\fB\-\-unstable\fR
.RS 4
Use an "unstable" hash as the patch ID\&. With this option, the result produced is compatible with the patch\-id value produced by git 1\&.9 and older and whitespace is ignored\&. Users with pre\-existing databases storing patch\-ids produced by git 1\&.9 and older (who do not deal with reordered patches) may want to use this option\&.
.sp
This is the default\&.
.RE
.SH "GIT"
.sp
Part of the \fBgit\fR(1) suite