git-futz

Fuzz Git commit timestamps & timezones

Installation

No installation is necessary, however if you put the script in your PATH, you could run the script as a custom Git command; e.g.

$ cp git-futz ~/bin/
$ git futz -h

Usage

Inside your repo before pushing your unpublished commits, run the script like this:

$ git-futz [--no-tz] [<last-public-commit>]

git-futz will rewrite the timestamps such that they are evenly distributed between the timestamp of the <last-public-commit> and now.

Optionally, it also assigns a timezone randomly, i.e. if you run it today it might choose London, and on a subsequent call tomorrow it could pick Tokyo. This however works only on Linux (needs: tzdata, find & shuf). If the tzdata database cannot be found, this feature is disabled.

If you want to disable the feature explicitly, you can pass the optional flag --no-tz.

Note that <last-public-commit> is optional. If it is not provided, the following heuristic will be applied to find the last public commit.

• identify remote associated to the current branch: my_remote

• find the remote head it is configured to merge with: refs/heads/branch

• find the last public commit using: my_remote/branch..HEAD; note the 2 dots, it means in the case of diverging histories, the last common ancestor will be picked

  1. straight line history: B, C, D will be rewritten

     public   private -->
        A ----- B ----- C ----- D
     

  2. diverging history: F, G, H will be rewritten

     A ----- B ----- C ----- D ----- E (public)
      \
       F ----- G ----- H
     private -->
     

Change log

• POC: works after some sed magic 🎉
  • depends on Python for date arithmetic 🙁
• Reimplement date arithmetic using integer maths in Bash 😉
• Add timezone randomisation
• Make timezone randomisation optional; improves portability ✨
• Bug fix: was reading commit timestamp with git-show instead of git-log 😶
• Preserve committer name & email 🥇
• Document various install options
• Add automatic upstream detection heuristic 🎁

FAQ

• Q: How can I run git-futz automatically before a git-push?

• A: You could write a git alias that runs git-futz before doing a push.

  [alias]
          futzy-push  =  !git futz && git push
  

• Q: Can I install the script as a git hook?

• A: Unfortunately currently I have not found a way to do this, since the script rewrites history, and the pre-push hook (see: .git/hooks/pre-push.sample) runs after determining the commits that should be pushed.

• Q: Can I schedule running git-futz and git-push to also not reveal when I ran the command?

• A: This is a bit tricky, I'm not certain yet what would be the best practice. Note that git-futz only alters the timestamp in the commit history. When you git-push, your remote forge (GitHub, GitLab, etc) can record the time.

  On GitHub, this is sometime shown as a notification on the repository page:

  @username pushed branch branch_name XYZ minutes ago

  I don't think this can be avoided. So to "poison" this information, you could schedule a cron job at your desired time. Something like this should work:

  cd /path/to/repo && git futz && git push