From: Jeff King <peff@peff.net>
To: Taylor Blau <me@ttaylorr.com>
Cc: Matt McCutchen <matt@mattmccutchen.net>, git@vger.kernel.org
Subject: Re: Renaming the "master" branch without breaking existing clones
Date: Mon, 3 Aug 2020 15:40:06 -0400 [thread overview]
Message-ID: <20200803194006.GA2715275@coredump.intra.peff.net> (raw)
In-Reply-To: <20200803160051.GA50799@syl.lan>
On Mon, Aug 03, 2020 at 12:00:51PM -0400, Taylor Blau wrote:
> This is more-or-less what I was proposing in the message that I linked
> above. Maybe a more solidified proposal might look something as follows:
>
> - We could introduce a mechanism to mark certain refs as aliases to
> other refs. For example, a remote might publish its
> 'refs/heads/master' as an alias to 'refs/heads/main', so that any
> reads or writes to the former get applied to the latter
> transparently.
I think symrefs do this already. Try this:
git init parent
git -C parent checkout -b main
git -C parent commit --allow-empty -m one
git -C parent symbolic-ref refs/heads/master refs/heads/main
git clone parent clone
cd clone
GIT_TRACE_PACKET=1 git ls-remote 2>&1 >/dev/null |
perl -lne '/git</ && /packet: (.*)/ and print $1'
Assuming you have the v2 protocol enabled, you should see:
git< 3ba9220cd714e9350cb4becd1cb56d0cacf29d9b HEAD symref-target:refs/heads/main
git< 3ba9220cd714e9350cb4becd1cb56d0cacf29d9b refs/heads/main
git< 3ba9220cd714e9350cb4becd1cb56d0cacf29d9b refs/heads/master symref-target:refs/heads/main
(if you don't you'll still see them as aliases, but you won't be told
that master is a symref).
And it even works for pushing. Doing:
git checkout -b master origin/master
git commit --allow-empty -m two
git push
updates both "main" and "master".
The real trick is that you can't create or update symbolic refs on the
server side using a client. So this would have to be something that
hosting providers allow (and there might be some security implications;
I'm not sure what happens if you create a loop in the symref
resolution).
> - A ref alias can be annotated to say "I am a transition ref alias",
> i.e., that clients should be taught to rename their copy of 'master'
> to 'main' (and update remote-tracking refs accordingly).
It's not specifically marked as a transition, but a client could act on
the symref advertisement above.
-Peff
next prev parent reply other threads:[~2020-08-03 19:40 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 12:15 Renaming the "master" branch without breaking existing clones Matt McCutchen
2020-08-03 16:00 ` Taylor Blau
2020-08-03 16:19 ` Junio C Hamano
2020-08-03 16:39 ` Taylor Blau
2020-08-03 19:40 ` Jeff King [this message]
2020-08-03 20:40 ` Junio C Hamano
2020-08-03 20:45 ` Jeff King
2020-08-03 21:02 ` Junio C Hamano
2020-08-03 21:11 ` Jeff King
2020-08-03 21:38 ` Junio C Hamano
2020-08-04 0:37 ` Matt McCutchen
2020-08-04 0:43 ` Matt McCutchen
2020-08-03 16:14 ` Junio C Hamano
2020-08-03 17:41 ` Matt McCutchen
2020-08-03 18:20 ` Kaartic Sivaraam
2020-08-03 18:47 ` Junio C Hamano
2020-08-04 8:50 ` Kaartic Sivaraam
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