| 1 | git-patch-id(1) |
| 2 | =============== |
| 3 | |
| 4 | NAME |
| 5 | ---- |
| 6 | git-patch-id - Compute unique IDs for patches |
| 7 | |
| 8 | SYNOPSIS |
| 9 | -------- |
| 10 | [synopsis] |
| 11 | git patch-id [--stable | --unstable | --verbatim] |
| 12 | |
| 13 | DESCRIPTION |
| 14 | ----------- |
| 15 | Read patches from standard input and compute the patch IDs. |
| 16 | |
| 17 | A "patch ID" is nothing but a sum of SHA-1 of the file diffs associated with a |
| 18 | patch, with line numbers ignored. As such, it's "reasonably stable", but at |
| 19 | the same time also reasonably unique, i.e., two patches that have the same |
| 20 | "patch ID" are almost guaranteed to be the same thing. |
| 21 | |
| 22 | The main usecase for this command is to look for likely duplicate commits. |
| 23 | |
| 24 | When dealing with `git diff-tree --patch` output, it takes advantage of |
| 25 | the fact that the patch is prefixed with the object name of the |
| 26 | commit, and outputs two 40-byte hexadecimal strings. The first |
| 27 | string is the patch ID, and the second string is the commit ID. |
| 28 | This can be used to make a mapping from patch ID to commit ID for a |
| 29 | set or range of commits. |
| 30 | |
| 31 | OPTIONS |
| 32 | ------- |
| 33 | |
| 34 | `--verbatim`:: |
| 35 | Calculate the patch ID of the input as it is given, do not strip |
| 36 | any whitespace. Implies `--stable` and forbids `--unstable`. |
| 37 | + |
| 38 | This is the default if `patchid.verbatim` is `true`. |
| 39 | |
| 40 | `--stable`:: |
| 41 | Use a "stable" sum of hashes as the patch ID. With this option: |
| 42 | + |
| 43 | -- |
| 44 | - Reordering file diffs that make up a patch does not affect the ID. |
| 45 | In particular, two patches produced by comparing the same two trees |
| 46 | with two different settings for `-O<orderfile>` result in the same |
| 47 | patch ID signature, thereby allowing the computed result to be used |
| 48 | as a key to index some meta-information about the change between |
| 49 | the two trees. |
| 50 | |
| 51 | - The result is different from the value produced by Git 1.9 and older |
| 52 | or produced when an "unstable" hash (see `--unstable` below) is |
| 53 | configured - even when used on a diff output taken without any use |
| 54 | of `-O<orderfile>`, thereby making existing databases storing such |
| 55 | "unstable" or historical patch IDs unusable. |
| 56 | |
| 57 | - All whitespace within the patch is ignored and does not affect the ID. |
| 58 | -- |
| 59 | + |
| 60 | This is the default if `patchid.stable` is set to `true`. |
| 61 | |
| 62 | `--unstable`:: |
| 63 | Use an "unstable" hash as the patch ID. With this option, |
| 64 | the result produced is compatible with the patch ID value produced |
| 65 | by Git 1.9 and older and whitespace is ignored. Users with pre-existing |
| 66 | databases storing patch IDs produced by Git 1.9 and older (who do not deal |
| 67 | with reordered patches) may want to use this option. |
| 68 | + |
| 69 | This is the default. |
| 70 | |
| 71 | EXAMPLES |
| 72 | -------- |
| 73 | |
| 74 | linkgit:git-cherry[1] shows what commits from a branch have patch ID |
| 75 | equivalent commits in some upstream branch. But it only tells you |
| 76 | whether such a commit exists or not. What if you wanted to know the |
| 77 | relevant commits in the upstream? We can use this command to make a |
| 78 | mapping between your branch and the upstream branch: |
| 79 | |
| 80 | ---- |
| 81 | #!/bin/sh |
| 82 | |
| 83 | upstream="$1" |
| 84 | branch="$2" |
| 85 | test -z "$branch" && branch=HEAD |
| 86 | limit="$3" |
| 87 | if test -n "$limit" |
| 88 | then |
| 89 | tail_opts="$limit".."$upstream" |
| 90 | else |
| 91 | since=$(git log --format=%aI "$upstream".."$branch" | tail -1) |
| 92 | tail_opts=--since="$since"' '"$upstream" |
| 93 | fi |
| 94 | for_branch=$(mktemp) |
| 95 | for_upstream=$(mktemp) |
| 96 | |
| 97 | git rev-list --no-merges "$upstream".."$branch" | |
| 98 | git diff-tree --patch --stdin | |
| 99 | git patch-id --stable | sort >"$for_branch" |
| 100 | git rev-list --no-merges $tail_opts | |
| 101 | git diff-tree --patch --stdin | |
| 102 | git patch-id --stable | sort >"$for_upstream" |
| 103 | join -a1 "$for_branch" "$for_upstream" | cut -d' ' -f2,3 |
| 104 | rm "$for_branch" |
| 105 | rm "$for_upstream" |
| 106 | ---- |
| 107 | |
| 108 | Now the first column shows the commit from your branch and the second |
| 109 | column shows the patch ID equivalent commit, if it exists. |
| 110 | |
| 111 | SEE ALSO |
| 112 | -------- |
| 113 | linkgit:git-cherry[1] |
| 114 | |
| 115 | GIT |
| 116 | --- |
| 117 | Part of the linkgit:git[1] suite |