Merge git://git.bogomips.org/git-svn

[git.git] / Documentation / git-patch-id.txt

diff --git a/Documentation/git-patch-id.txt b/Documentation/git-patch-id.txt
index 9a4abd1..5389097 100644 (file)
--- a/Documentation/git-patch-id.txt
+++ b/Documentation/git-patch-id.txt
@@ -3,26 +3,31 @@ git-patch-id(1)
 
 NAME
 ----
-git-patch-id - Some git command not yet documented.
-
+git-patch-id - Generate a patch ID
 
 SYNOPSIS
 --------
-'git-patch-id' [ --option ] <args>...
+'git-patch-id' < <patch>
 
 DESCRIPTION
 -----------
-Does something not yet documented.
+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 string.  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
 -------
---option::
-       Some option not yet documented.
-
-<args>...::
-       Some argument not yet documented.
-
+<patch>::
+       The diff to create the ID of.
 
 Author
 ------
@@ -34,5 +39,5 @@ Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
 
 GIT
 ---
-Part of the link:git.html[git] suite
+Part of the gitlink:git[7] suite