git/Documentation/git-patch-id.txt

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

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

SYNOPSIS
--------
'git patch-id' < <patch>

DESCRIPTION
-----------
A "patch ID" is nothing but a SHA1 of the diff 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
-------
<patch>::
	The diff to create the ID of.

Author
------
Written by Linus Torvalds <torvalds@osdl.org>

Documentation
--------------
Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.

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