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