Re: [PATCH] Disallow creating ambiguous branch names by default

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 17, 2011, 18:41 UTC
Message-ID: <7vhb5fev8a.fsf@alter.siamese.dyndns.org>
In-Reply-To: <1313569298-3879-1-git-send-email-conrad.irwin@gmail.com>

Conrad Irwin <conrad.irwin@gmail.com> writes:

> Before this change, it was comparatively easy to create a confusingly

Drop everything before the ", ".

> named branch (like "origin/master" or "tag.1"). The former case is
> particularly biting to newcomers, who suddenly find themselves needing
> to handle nuances of the refs namespaces.

If you start forbidding certain names, newcomers will need to be exposed the same nuances to understand why what they wanted to do is not allowed, so that is not an argument.

My preferences (take them as "the ground rules" if you want) are:

 - We don't disallow what we have long allowed, without a good reason;
 - We make sure new people will get a warning with useful advice.

I would be happy to see the end result that warns when the end user creates a branch (or a tag) that is ambiguous _when_ it is created (not "much later, when we noticed there are ambiguous refs"), and offers an advice message to use "branch -m" to rename it away (control the message with a new "advice.*" configuration and unless explicitly declined with it, always give the advice).

> In both cases, git commands would omit a warning about "ambiguous refs"
> if they noticed that this had occurred,

Assuming that you meant s/omit/emit/, I do agree that what we do right now is suboptimal. I just tried these two:

	$ git branch v1.0.0
        $ git checkout v1.0.0
        warning: refname 'v1.0.0' is ambigous.
	$ git branch -m v1.0.0-branch

        $ git checkout -b v1.0.0
        Switched to a new branch 'v1.0.0'
	$ git checkout v1.0.0
        warning: refname 'v1.0.0' is ambigous.
	Already on 'v1.0.0'
	$ git branch -m v1.0.0-branch-2

We should be giving these warning messages immediately after creating potentially problematic refs, i.e. just after "git branch v1.0.0" and "git checkout -b v1.0.0". The user experience should look like this instead:

	$ git branch v1.0.0
        warning: refname 'v1.0.0' is ambiguous.
        advice: you may want to rename it to an unambigous name with
        advice: git branch -m v1.0.0 v1.0.0-branch
	$ git branch -m v1.0.0 v1.0.0-branch ;# thanks for an advice

        $ git checkout -b v1.0.0
        warning: refname 'v1.0.0' is ambiguous.
        advice: you may want to rename it to an unambigous name with
        advice: git branch -m v1.0.0-branch-2
	$ git branch -m v1.0.0-branch-2 ;# thanks for an advice