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
· 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.
The diff to create the ID of.
This page is part of the git (Git distributed version control system)
project. Information about the project can be found at
⟨http://git-scm.com/⟩. If you have a bug report for this manual page,
see ⟨http://git-scm.com/community⟩. This page was obtained from the
project's upstream Git repository ⟨https://github.com/git/git.git⟩ on
2017-03-13. If you discover any rendering problems in this HTML ver‐
sion of the page, or you believe there is a better or more up-to-date
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information in this COLOPHON (which is not part of the original man‐
ual page), send a mail to firstname.lastname@example.org
Git 22.214.171.1249.ge5da865 12/05/2015 GIT-PATCH-ID(1)