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git-patch-id(1)


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.

   <patch>
       The diff to create the ID of.

GIT

   Part of the git(1) suite



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