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bfd125f64f
Emphasize that you can pass multiple patches or diffs to this command.
git-patch-id(1) is an efficient pID–commit mapper, able to map
thousands of commits in seconds. But discussions on the command
seem to typically[1] use the standard loop-over-rev-list-and-
shell-out pattern:
for commit in rev-list:
prepare a diff from commit | git patch-id
This is unnecessary; we can bulk-process the patches:
git rev-list --no-merges <ref> |
git diff-tree --patch --stdin |
git patch-id --stable
The first version (translated to shell) takes a little over nine
minutes for a commit history of about 78K commits.[2] The other one,
by contrast, takes slightly less than a minute.
Also drop “the” from “standard input”.
† 1: https://stackoverflow.com/a/19758159
† 2: This is `master` of this repository on 2025-10-02
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
74 lines
2.5 KiB
Plaintext
74 lines
2.5 KiB
Plaintext
git-patch-id(1)
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===============
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NAME
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----
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git-patch-id - Compute unique IDs for patches
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SYNOPSIS
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--------
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[synopsis]
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git patch-id [--stable | --unstable | --verbatim]
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DESCRIPTION
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-----------
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Read patches from standard input and compute the patch IDs.
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A "patch ID" is nothing but a sum of SHA-1 of the file diffs associated with a
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patch, with line numbers ignored. As such, it's "reasonably stable", but at
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the same time also reasonably unique, i.e., two patches that have the same
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"patch ID" are almost guaranteed to be the same thing.
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The main usecase for this command is to look for likely duplicate commits.
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When dealing with `git diff-tree --patch` output, it takes advantage of
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the fact that the patch is prefixed with the object name of the
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commit, and outputs two 40-byte hexadecimal strings. The first
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string is the patch ID, and the second string is the commit ID.
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This can be used to make a mapping from patch ID to commit ID for a
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set or range of commits.
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OPTIONS
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-------
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`--verbatim`::
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Calculate the patch ID of the input as it is given, do not strip
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any whitespace. Implies `--stable` and forbids `--unstable`.
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+
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This is the default if `patchid.verbatim` is `true`.
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`--stable`::
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Use a "stable" sum of hashes as the patch ID. With this option:
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+
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--
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- Reordering file diffs that make up a patch does not affect the ID.
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In particular, two patches produced by comparing the same two trees
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with two different settings for `-O<orderfile>` result in the same
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patch ID signature, thereby allowing the computed result to be used
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as a key to index some meta-information about the change between
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the two trees.
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- The result is different from the value produced by Git 1.9 and older
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or produced when an "unstable" hash (see `--unstable` below) is
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configured - even when used on a diff output taken without any use
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of `-O<orderfile>`, thereby making existing databases storing such
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"unstable" or historical patch IDs unusable.
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- All whitespace within the patch is ignored and does not affect the ID.
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--
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+
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This is the default if `patchid.stable` is set to `true`.
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`--unstable`::
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Use an "unstable" hash as the patch ID. With this option,
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the result produced is compatible with the patch ID value produced
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by Git 1.9 and older and whitespace is ignored. Users with pre-existing
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databases storing patch IDs produced by Git 1.9 and older (who do not deal
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with reordered patches) may want to use this option.
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+
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This is the default.
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GIT
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---
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Part of the linkgit:git[1] suite
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