git-patch-id(1)
===============

NAME
----
git-patch-id - Compute unique ID for a patch

SYNOPSIS
--------
[verse]
'git patch-id' [--stable | --unstable] < <patch>

DESCRIPTION
-----------
A "patch ID" is nothing but a sum of SHA-1 of the diff hunks associated with a
patch, with whitespace and line numbers ignored.  As such, it's "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.

IOW, you can use this thing to look for likely duplicate commits.

When dealing with 'git diff-tree' 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.

OPTIONS
-------

--stable::
	Use a symmetrical sum of hashes as the patch ID.
	With this option, reordering file diffs that make up a patch or
	splitting a diff up to multiple diffs that touch the same path
	does not affect the ID.
	This is the default.

--unstable::
	Use a non-symmetrical sum of hashes, such that reordering
	or splitting the patch does affect the ID.
	This was the default value for git 1.9 and older.

<patch>::
	The diff to create the ID of.

GIT
---
Part of the linkgit:git[1] suite
