From: Thomas Rast <trast@student.ethz.ch>
Date: Thu, 29 Oct 2009 16:43:39 GMT
Subject: Re: date change of commit?
Message-ID: <200910291743.53701.trast@student.ethz.ch>
In-Reply-To: <4AE9AAE7.2080404@dawes.za.net>

Rogan Dawes wrote:
> Alex K wrote:
> > And how do you actually set those variables? Sorry to ask such a
> > trivial question but it's been an hour that i'm going through the doc
> > for such a simple feature. I thought those were environment variables
> 
> As you suspected, they are environment variables.
> 
> i.e. :
> 
> $ GIT_AUTHOR_DATE="1112911993 -0700" git commit x

Since this was in the context of git-filter-branch, I should point out
that you'll have to use the variables with --env-filter and (like the
manpage says) make sure you export them.

So to change the date of a single commit with SHA1 <sha1>, you could
say

git filter-branch --env-filter '
  if [ $GIT_COMMIT = <sha1> ]; then
    export GIT_AUTHOR_DATE="1112911993 -0700"
    export GIT_COMMITTER_DATE="1112911993 -0700"
  fi
' <other_arguments>

Alex K wrote:
> for such a simple feature

I'm not sure if you're referring to setting the variables or actually
rewriting the commits here, but anyway:

The reason why the latter is so hard is that rewriting "old" history
is a _huge_ hassle for people who already have the previous version of
that history.

That being said, _why_?  The dates are never a guarantee that
something happened earlier or later precisely because they can easily
be modified at commit time.  So nobody should take them as more than a
hint, and there's little use in faking hints.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch