From: Phillip Wood <phillip.wood123@gmail.com>
Date: Mon, 17 Apr 2023 12:14:27 GMT
Subject: Re: Should --update-refs exclude refs pointing to the current HEAD?
Message-ID: <98548a5b-7d30-543b-b943-fd48d8926a33@gmail.com>
In-Reply-To: <adb7f680-5bfa-6fa5-6d8a-61323fee7f53@haller-berlin.de>

Hi Stefan

On 17/04/2023 09:21, Stefan Haller wrote:
> The --update-refs option of git rebase is so useful that I have it on by
> default in my config. For stacked branches I find it hard to think of
> scenarios where I wouldn't want it.
> 
> However, there are cases for non-stacked branches (i.e. other branches
> pointing at the current HEAD) where updating them is undesirable. In
> fact, pretty much always, for me. Two examples, both very similar:
> 
> 1. I have a topic branch which is based off of master; I want to make a
> copy of that branch and rebase it onto devel, just to try if that would
> work. I don't want the original branch to be moved along in this case.
> 
> 2. I have a topic branch, and I want to make a copy of it to make some
> heavy history rewriting experiments. Again, my interactive rebases would
> always rebase both branches in the same way, not what I want. In this
> case I could work around it by doing the experiments on the original
> branch, creating a tag beforehand that I could reset back to if the
> experiments fail. But maybe I do want to keep both branches around for a
> while for some reason.
> 
> Both of these cases could be fixed by --update-refs not touching any
> refs that point to the current HEAD.

I'd use a detached HEAD for the "experimental" rebase and then update 
the branch if the rebase was successful. If you really want to use 
another branch you could try running "git commit --amend --only" before 
rebasing to update the commit date so the two branches don't point to 
the same commit.

We could add a command line option to restrict the branches that are 
updated by --update-refs but I'm not that enthusiastic about it.

> I'm having a hard time coming up
> with cases where you would ever want those to be updated, in fact.

If a user using stacked branches creates a new branch and then realizes 
they need to fix something on the parent before creating any commits on 
the new branch they would want both to be updated. e.g.	
	$ git symbolic-ref HEAD
	refs/heads/topic
	$ git checkout -b another-topic
	# fix a bug in topic - want topic and another-topic to be
	# updated
	$ git rebase -i --update-refs HEAD~2

Best Wishes

Phillip

> Any opinions?
> 
> -Stefan
>