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:
o 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;
o 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
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 2.15.0 10/30/2017 GIT-PATCH-ID(1)