Re: [PATCH v4] Introduce %<branch> as shortcut to the tracked branch

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 20, 2009, 17:03 UTC
Message-ID: <7v7i2ki0sw.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <alpine.DEB.1.00.0903201714020.10279@pacific.mpi-cbg.de>

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

Show 11 quoted lines

> Often, it is quite interesting to inspect the branch tracked by a given
> branch.  This patch introduces a nice notation to get at the tracked
> branch: '%<branch>' can be used to access that tracked branch.
>
> A special shortcut '%' refers to the branch tracked by the current branch.
>
> Suggested by Pasky.
>
> Even if a branch name can legally start with a '%' sign, we can use the
> special character '%' here, as you can always specify the full ref:
> refs/heads/%my-branch (pointed out by doener on IRC).

That is not a good argument, as %<name> is (just like name@{-n} is) a substitute way to spell the "name" of a branch, not just a random SHA-1, and to some commands it makes a difference between <branchname> and refs/heads/<branchname>. The latter is not giving the name of the branch, but merely a commit object name.

An most obvious one is that "git checkout branchname" and "git checkout refs/heads/branchname" behave differently. You cannot checkout a branch called %master after this patch goes in.

Just be honest and say "You may have a branch whose name begins with a '%' and you cannot refer to it anymore in certain contexts. Too bad. Don't do it next time you create a new branch". I _can_ buy that argument.

It however asks for a sane escape hatch. You cannot "fix" such branch names in most obvious ways (if you could, that would be a bug in this % feature).

 (1) git branch -m %master percent-master

     We would end up renaming what master tracks to new name.

 (2) git branch percent-master refs/heads/%master; git branch -d %master

     The first part is a good try, but the latter deletes what master
     tracks.

"git update-ref -d refs/heads/%master" needs to replace the second step of the latter.