Truncate dates and drop timezones in git commits

These hooks modify the author date and committer date of any commit. An example:

$ git commit -m 'tmp'
date-truncate: 885c484 -> 546299f (truncated author date and committer date)
  (use "git reset 885c484" to undo)
[master 885c484] tmp
 1 file changed, 5 insertions(+)
 create mode 100644 tmp-file

When a commit is made, the author date and committer date are automatically truncated to the date part only, and the timezone information is dropped. The commit hash is changed as a result.

The old commit: (which will not be published if you run git push)

$ git show --format=fuller 885c484
commit 885c484cfc724dd7f4f087c08859b14019eaf3f9
Author:     Hypercube <hypercube@0x01.me>
AuthorDate: Mon Apr 1 11:01:44 2024 +0800
Commit:     Hypercube <hypercube@0x01.me>
CommitDate: Mon Apr 1 11:01:44 2024 +0800

    tmp

The new commit:

$ git show --format=fuller 546299f
commit 546299f946aac739d9ec6a8229434fb0be35963d (HEAD -> master)
Author:     Hypercube <hypercube@0x01.me>
AuthorDate: Mon Apr 1 00:00:00 2024 +0000
Commit:     Hypercube <hypercube@0x01.me>
CommitDate: Mon Apr 1 00:00:00 2024 +0000

    tmp

How it works

The git-date-truncate script inspects the last commit, if its author name and author email matches user.name and user.email in the git configuration, it drops the time and timezone information from the author date. The same is done for the committer.

The hooks call the script after a commit is made. By default, it will output the old and new commit hashes, and a command to undo the operation, in case the user wants to revert the changes.

Installation

1. Copy the git-date-truncate script to somewhere in your $PATH.
2. Copy the files in hooks directory to .config/git/template/hooks or ~/.git-template/hooks. If you only want to enable the hooks for a single repository, copy the files to .git/hooks in the repository.
3. For all existing repositories, run git init in the repository to apply the hooks in the template directory.

Disclaimer

This script is not tested with all possible edge cases. Use at your own risk. In rare cases like complex rebases, the script may not work as expected.