git-patch-id - Online in the Cloud

PROGRAM:

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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