1git-patch-id(1) 2=============== 3 4NAME 5---- 6git-patch-id - Compute unique ID for a patch 7 8SYNOPSIS 9-------- 10[verse] 11'git patch-id' [--stable | --unstable] 12 13DESCRIPTION 14----------- 15Read a patch from the standard input and compute the patch ID for it. 16 17A "patch ID" is nothing but a sum of SHA-1 of the file diffs associated with a 18patch, with whitespace and line numbers ignored. As such, it's "reasonably 19stable", but at the same time also reasonably unique, i.e., two patches that 20have the same "patch ID" are almost guaranteed to be the same thing. 21 22IOW, you can use this thing to look for likely duplicate commits. 23 24When dealing with 'git diff-tree' output, it takes advantage of 25the fact that the patch is prefixed with the object name of the 26commit, and outputs two 40-byte hexadecimal strings. The first 27string is the patch ID, and the second string is the commit ID. 28This can be used to make a mapping from patch ID to commit ID. 29 30OPTIONS 31------- 32 33--stable:: 34 Use a "stable" sum of hashes as the patch ID. With this option: 35 - Reordering file diffs that make up a patch does not affect the ID. 36 In particular, two patches produced by comparing the same two trees 37 with two different settings for "-O<orderfile>" result in the same 38 patch ID signature, thereby allowing the computed result to be used 39 as a key to index some meta-information about the change between 40 the two trees; 41 42 - Result is different from the value produced by git 1.9 and older 43 or produced when an "unstable" hash (see --unstable below) is 44 configured - even when used on a diff output taken without any use 45 of "-O<orderfile>", thereby making existing databases storing such 46 "unstable" or historical patch-ids unusable. 47 48 This is the default if patchid.stable is set to true. 49 50--unstable:: 51 Use an "unstable" hash as the patch ID. With this option, 52 the result produced is compatible with the patch-id value produced 53 by git 1.9 and older. Users with pre-existing databases storing 54 patch-ids produced by git 1.9 and older (who do not deal with reordered 55 patches) may want to use this option. 56 57 This is the default. 58 59<patch>:: 60 The diff to create the ID of. 61 62GIT 63--- 64Part of the linkgit:git[1] suite