Re: Converting repo from HG, `git filter-branch --prune-empty -- --all` is extremely slow and errors out.

From: Felipe Contreras <felipe.contreras@gmail.com>
Date: Sep 13, 2013, 00:47 UTC
Message-ID: <CAMP44s1cmcfSuB-TnFL+-57i5W=EA8v322rVDoUELCPF948jPw@mail.gmail.com>
In-Reply-To: <D4C9DBA5F955904683C89B4A96DA7759EA78D60FDF@synapsemail>

On Thu, Sep 12, 2013 at 5:01 PM, John Gietzen <jgietzen@woot.com> wrote:

Show 8 quoted lines

> Background:
> Windows, git version 1.8.3.msysgit.0
> bare repo, 54k commits after migration from HG
> git filter-branch --prune-empty -- --all
>
> I'm trying to clean up our repository after migrating it from HG.  I'm running the filter-branch command listed above in an effort to clean up all of garbage commits that HG required ("closing branch" commits and their ilk).
>
> From my past experience, "git filter-branch" is extremely quick when using simple filters, like env-filter, since it doesn't have to touch the working dir.  However, in our case each revision is taking 1-3 seconds; our entire repo will take 30 hours to clean up at this rate.  Normally, this wouldn't be a problem, except that we are getting "sh.exe couldn't start" errors after anywhere between the 5000th and 6000th rewritten commit.  Filter-branch doesn't have support for picking up where it left off, so we are entirely unable to clean up our repo.

Indeed, I remember writing my own simplified version of 'git filter-branch' that was much faster. If I recall correctly, the trick was avoiding 'git write-tree' which can be done if you are not using any tree filter, but 'git filter-branch' is not that smart.

If all you want to do is prune empty commits, it should be easy to write a script that simply does 'git commit-tree'. I might decide to do that based on my script if I have time today.

-- 
Felipe Contreras