Re: master^ is not a local branch -- huh?!?

From: Ron Garret <ron1@flownet.com>
Date: Feb 2, 2010, 00:45 UTC
Message-ID: <ron1-9A9CEA.16452601022010@news.gmane.org>
In-Reply-To: <20100202001530.GL9553@machine.or.cz>

In article <20100202001530.GL9553@machine.or.cz>,
 Petr Baudis <pasky@suse.cz> wrote:

Show 20 quoted lines

> On Mon, Feb 01, 2010 at 03:56:31PM -0800, Ron Garret wrote:
> > In article <7vwrywplxz.fsf@alter.siamese.dyndns.org>,
> >  Junio C Hamano <gitster@pobox.com> wrote:
> > > Ron Garret <ron1@flownet.com> writes:
> > > > And as long as I'm weighing in, it would also help to prevent confusion 
> > > > if it were made clear that this unnamed branch doesn't actually come 
> > > > into existence unless and until you do a commit.
> > > 
> > > This shows that you are still thinking a branch is a line (or multiple
> > > lines).  It is not.
> > 
> > The git user's guide says it is:
> > 
> > "When we need to be precise, we will use the word "branch" to mean a 
> > line of development..."
> > 
> > But I understand that a branch is not necessarily a line.  In general 
> > it's a DAG.  I get that.
> 
> Again, no. In the most narrow sense, "branch == branch head".

The manual specifically contradicts you, so either you are wrong or the manual is wrong.

Don't forget that what is at issue here is not how git works (I'm pretty sure everyone is on the same page about that) but how to explain it to someone who is not already familiar with it. So it's important to use terminology that is consistent with what the manual says.

> Branch is just a pointer.

No, a branch is not "just" a pointer. At the very least it's a pointer with a name. The SHA1 hash of a blob is a pointer too. But it's not a branch. The SHA1 hash of a commit is a pointer too, but if you were to consider that a branch then "branch" would simply become synonymous with "commit" and the term would lose its utility.

> Which is the reason why your original statement does not
> make sense.

That remains to be seen. I believe that on the manual's definition of "branch" my statement not only makes sense, but is actually correct.

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> We could say that the "branch closure" is the DAG of ancestry of the
> commit we point to. We use "branch" in that sense since we have to
> express ourselves in natural language, we are not in a calculus class,
> there is mapping to various real-world and other-VCS concepts in play,
> etc. But in order to use "branch" in the ambiguous sense, you should
> first realize what it means in the _strict_ sense, so that you
> understand the texts correctly and don't reach wrong conclusions or
> create invalid concepts like "branches coming into existence". :-)

I am trying to be as strict as I can according to what is in the documentation.

rg