vanity-git-commit

Modify an Git commit to have a desired short commit ID

This little Python script takes the HEAD commit from a local Git repository and tries to recreate an almost identical commit whose commit ID starts with a user-defined value. It does so by salting the commit data. Since this is a brute-force process, it runs in parallel on all CPU cores. Like vanity license plates, these new commit IDs serve no practical purpose other than to look cool.

Example:

$ git log -n1
commit a84d66cd16025055005126a326a7ad923c5de804 (HEAD -> master)
Author: Christian Zietz <czietz@xxx.invalid>
Date:   Sun Dec 27 10:53:12 2020 +0000

    Hide salt in metadata

    This makes it invisble in 'git log', 'git show', or on GitHub.
    It's unknown if this breaks any third-party Git tools.
    Use at your own risk!

$ py vanity.py 4242420
4242420c6d62111bf65fed8178795360e214d251
HEAD is now at 4242420 Hide salt in metadata

$ git log -n1
commit 4242420c6d62111bf65fed8178795360e214d251 (HEAD -> master)
Author: Christian Zietz <czietz@xxx.invalid>
Date:   Sun Dec 27 10:53:12 2020 +0000

    Hide salt in metadata

    This makes it invisble in 'git log', 'git show', or on GitHub.
    It's unknown if this breaks any third-party Git tools.
    Use at your own risk!

Notes:

This is merely a toy program. I got the idea while reading about how Git objects work.
Surely, it could be optimized more.
The longer the desired prefix is, the longer it will take to find a solution and the more likely it'll be that no solution can be found at all. However, the 7 character short commit IDs used by GitHub can be brute-forced in a few minutes on a modern machine. For an example, see https://github.com/czietz/vanity-git-commit/commit/1234567.
If you want to undo the change, you can use git reflog to find the previous, i.e., unsalted commit ID, or you can immediately revert it with git reset --hard HEAD@{1}.
Use at your own risk!

czietz/vanity-git-commit

vanity-git-commit