GIT-PATCH-ID(1)                    Git Manual                    GIT-PATCH-ID(1)

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

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

       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.

           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.

           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.

       Part of the git(1) suite

Git 2.30.0                         12/28/2020                    GIT-PATCH-ID(1)