Re: [PATCH] refs.c: interpret @ as HEAD

Duy Nguyen [off-list ref] writes:

It's not hard to do. The below patch makes "." equivalent to HEAD and
".U" -> "@{u}". Refs are not supposed to have '.' at the beginning, so
it's easy ...

How is the equivalent of master..@{u} expressed?  master...U?  How is
it disambiguated from a symmetric difference between master and U?

There are reasons why some characters are forbidden from appearing
at certain places in refname component. Anybody who designs a new
syntax needs to think _why_.

The restriction that a @ in refname cannot be followed by { is for
the same kind of disambiguation.  I do not mind a way to spell HEAD
with shorter than 4 keystrokes, and as I said I suspect "@" may be
the least bad one among what people may come up with in this thread,
but I do not think we can explain it as "@ is a synonym to HEAD"
[*1*].  We need to see if we can make the explanation we will give
to end users is understandable.


[Footnote]

*1* I do not think "@ is a new synonym for HEAD" would not be a good
explanation.  Some questions you should ask yourselves to see why:

"git update-ref HEAD $commit" is accepted.  If @ is a synonym for
HEAD, "git update-ref @ $commit" should work exactly the same way,
but is it desirable?  Would we have $GIT_DIR/@ as the result?  How
about "git symbolic-ref"?  Would @@{4} and HEAD@{4} be the same?