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795d41db13
The utility and usability of git-patch-id(1) was discussed
relatively recently:[1]
Using "git patch-id" is definitely in the "write a script for it"
category. I don't think I've ever used it as-is from the command
line as part of a one-liner. It's very much a command that is
designed purely for scripting, the interface is just odd and baroque
and doesn't really make sense for one-liners.
The typical use of patch-id is to generate two *lists* of patch-ids,
then sort them and use the patch-id as a key to find commits that
look the same.
The command doc *could* use an example, and since it is a mapper command
it makes sense for that example to be a little script.
Mapping the commits of some branch to an upstream ref allows us to
demonstrate generating two lists, sorting them, joining them, and
finally discarding the patch ID lookup column with cut(1).
† 1: https://lore.kernel.org/workflows/CAHk-=wiN+8EUoik4UeAJ-HPSU7hczQP+8+_uP3vtAy_=YfJ9PQ@mail.gmail.com/
Inspired-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
114 lines
3.6 KiB
Plaintext
114 lines
3.6 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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EXAMPLES
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--------
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linkgit:git-cherry[1] shows what commits from a branch have patch ID
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equivalent commits in some upstream branch. But it only tells you
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whether such a commit exists or not. What if you wanted to know the
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relevant commits in the upstream? We can use this command to make a
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mapping between your branch and the upstream branch:
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----
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#!/bin/sh
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upstream="$1"
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branch="$2"
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test -z "$branch" && branch=HEAD
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limit="$3"
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if test -n "$limit"
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then
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tail_opts="$limit".."$upstream"
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else
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since=$(git log --format=%aI "$upstream".."$branch" | tail -1)
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tail_opts=--since="$since"' '"$upstream"
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fi
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for_branch=$(mktemp)
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for_upstream=$(mktemp)
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git rev-list --no-merges "$upstream".."$branch" |
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git diff-tree --patch --stdin |
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git patch-id --stable | sort >"$for_branch"
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git rev-list --no-merges $tail_opts |
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git diff-tree --patch --stdin |
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git patch-id --stable | sort >"$for_upstream"
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join -a1 "$for_branch" "$for_upstream" | cut -d' ' -f2,3
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rm "$for_branch"
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rm "$for_upstream"
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----
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Now the first column shows the commit from your branch and the second
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column shows the patch ID equivalent commit, if it exists.
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GIT
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---
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Part of the linkgit:git[1] suite
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