Re: [PATCH v3] Add new @ shortcut for HEAD

From: Junio C Hamano <gitster@pobox.com>
Date: May 1, 2013, 22:08 UTC
Message-ID: <7vsj264am4.fsf@alter.siamese.dyndns.org>
In-Reply-To: <CAMP44s16X8c_5GgW=ZcA9wrd=oHAiVDZFWxqiGmysaUJckZ5wQ@mail.gmail.com>

Felipe Contreras <felipe.contreras@gmail.com> writes:

Show 20 quoted lines

> On Wed, May 1, 2013 at 12:53 PM, Junio C Hamano <gitster@pobox.com> wrote:
>> Felipe Contreras <felipe.contreras@gmail.com> writes:
>>
>>> So HEAD@{0}~0^0 is too much to type, but we can remove '^0', and we can
>>> remove '~0', and we can remove 'HEAD', which leaves us with @{0}, but we
>>> can't remove '{0}'?
>>>
>>> This patch allows '@' to be the same as 'HEAD'.
>>
>> While the above reasoning is cute, it is misleading.
>>
>> If you start from HEAD@{1}~0^0, we can remove '^0', we can remove
>> '~0', but you cannot remove HEAD from the remaining "HEAD@{1}"
>> without changing what it means.  @{1} is where the current branch
>> was, while HEAD@{1} is where you were---they are different when you
>> have just did "git checkout anotherbranch".  HEAD@{1} is the tip of
>> your previous branch, @{1} is where anotherbranch was before its tip
>> became the commit you have checked out.
>
> Replace @{1} with @{u} and it holds.

Yes and no. Starting from HEAD@{u}~0^0, we can remove ^0 and ~0, and you remove HEAD from the remaining "HEAD@{u}" to get @{u} and all of them still mean the same thing. It is the other branch your current branch is integrating with.

But that decomposition does not get you to HEAD which is the final destination you want to reach. As soon as you drop the remaining {u}, it suddenly changes the meaning and start referring to the current branch.

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>> So I'd suggest toning it down, perhaps something like this:
>>
>>         Even though we often can do without having to type "HEAD",
>>         e.g. "git log origin.." substitutes missing RHS with "HEAD",
>>         sometimes we still do need to type "HEAD" (thats six f*cking
>>         keystrokes "Caps Lock", "H", "E", "A", "D" and finally "Caps
>>         Lock").
>
> I don't know what RHS means, and I don't use caps lock :)

"right hand side"? You can say "Hold down Shift", H, E, A, D and "Release Shift" ;-).

>>         That is four keystrokes too many to name an often needed
>>         reference.  Make "@" usable as its synonym.
>
> Yeah, that's nice, but doesn't explain why "@", and why not something else.

The thing is, HEAD@{0}~0^0 nor HEAD@{u}~0^0 is not a valid explanation why it is "@", either.

But that does _not_ mean "@" is a good choice. Nor the explanation has to be based on the "starting from this and strip" progression.

"@" is already special and is familiar to users when specifying a ref, and that is a good enough reason (you can of course say that in the log message).