NAME

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

SYNOPSIS

       git patch-id [--stable | --unstable]

DESCRIPTION

       Read a patch from the standard input and compute the patch ID for it.

       A "patch ID" is nothing but a sum of SHA-1 of the file diffs 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 "stable" sum of hashes as the patch ID. With this option:

           •   Reordering file diffs that make up a patch does not affect the ID. In particular,
               two patches produced by comparing the same two trees with two different settings
               for "-O<orderfile>" result in the same patch ID signature, thereby allowing the
               computed result to be used as a key to index some meta-information about the
               change between the two trees;

           •   Result is different from the value produced by git 1.9 and older or produced when
               an "unstable" hash (see --unstable below) is configured - even when used on a diff
               output taken without any use of "-O<orderfile>", thereby making existing databases
               storing such "unstable" or historical patch-ids unusable.

                   This is the default if patchid.stable is set to true.

       --unstable
           Use an "unstable" hash as the patch ID. With this option, the result produced is
           compatible with the patch-id value produced by git 1.9 and older. Users with
           pre-existing databases storing patch-ids produced by git 1.9 and older (who do not
           deal with reordered patches) may want to use this option.

               This is the default.

GIT

       Part of the git(1) suite