Subject: Re: [PATCH] builtin-branch - allow deleting a fully specified branch-name

From: Junio C Hamano <[email-masked]>
Date: Thu, 09 Apr 2009 20:18:01 -0700

Mark Levedahl <[email-masked]> writes:

> On Thursday 09 April 2009 20:39:46 Junio C Hamano wrote:
>> Mark Levedahl <[email-masked]> writes:
>> > This change allows, for instance
>> > 	git branch -d refs/heads/foo
>> > to succeed. Without this patch, the code just assumes that the
>> > given branch name should be appended to "refs/heads" or
>> > "refs/remotes", thus attempting (and failing) in the above case
>> > to delete "refs/heads/refs/heads/foo"
>>
>> Your logic is broken.
>>
>> Why doesn't the user simply say "git branch -d foo"?  The command takes
>> "the branch name", not "arbitrary ref name".
>
> 1) git branch -d refs/<whatever> used to work,  I haven't bisected to find 
> when this stopped working, but the change broke one of my scripts, so this is 
> not new behavior, it is restoration of previous behavior.

I need to look at the history, if that is the case then perhaps Ok.

> 2) If I create branch  refs/frotz/bar , how do I ever delete it?

By this you must mean .git/refs/heads/refs/frotz/bar, right?  Then
shouldn't "git branch -d refs/frotz/bar" just work as is?  If you are
talking about .git/refs/frotz/bar, "git branch" should not touch it, it is
not even a branch.

> Also, the following all work

> 3) git branch refs/heads/foo
> 4) git branch -m refs/heads/foo refs/heads/bar 

If you mean it creates .git/refs/heads/refs/heads/foo, then sure it
should.  If it creates .git/refs/heads/foo, I think it is broken.

> 5) git  [checkout|pull|push|fetch|show] refs/heads/foo

Among these, checkout is the only special case that can take "branch name"
to switch branches.  Everything else takes extended SHA-1 expression.
Checkout can interpret the first argument as "branch to switch to", but it
does not necessarily so---think "detached HEAD", and also think "checking
out paths out of tree-ish".

> So, why is "git branch -d" so special?

"git branch -d", "git branch -m" and friends all take branch name, and as
such it can use "@{-1}" to _name_ 'the previous branch".  In that context,
you are _not_ naming the commit at the tip of the branch.  You are naming
the branch itself.

All other commands happen to take a branch name because that is just one
case of extended SHA-1 expression to name an object.  In that context, a
refname (which a branch name is a special case of) refers to the commit
pointed by it.  E.g.

        "git checkout HEAD~20 -- Makefile"
        "git show refs/heads/foo"
        "git show heads/foo"
        "git show foo"