Re: [PATCH 5/5] refs.c: make @ a pseudo-ref alias to HEAD

> First, make sure that check_refname_format() rejects the a refname
> beginning with a '@'.  Add a test to t1400 (update-ref) demonstrating
> that update-ref forbids the user from updating a ref named "@".
>
> Now, resolve_ref_unsafe() is built to resolve any refs that have a
> corresponding file inside $GITDIR.  Our "@" ref is a special
> pseudo-ref and does not have a filesystem counterpart.  So,
> hard-interpret "@" as "HEAD" and resolve .git/HEAD as usual.  This
> means that we can drop the 'git symbolic-ref @ HEAD' line in t1508
> (at-combinations), and everything will continue working as usual.
>
> If the user does manage to create a '.git/@' unsafely (via
> symbolic-ref or otherwise), it will be ignored.
>
> In practice, this means that you will now be able to do:
>
>     $ git show @~1
>     $ git log @^2
>
> Advertise these features in the tests and documentation.
>
> Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
> ---
>  Documentation/git-check-ref-format.txt |  2 ++
>  Documentation/revisions.txt            |  8 ++++++--
>  refs.c                                 | 12 ++++++++++--
>  t/t1400-update-ref.sh                  |  3 +++
>  t/t1508-at-combinations.sh             |  7 ++++---
>  5 files changed, 25 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/git-check-ref-format.txt b/Documentation/git-check-ref-format.txt
> index ec1739a..3de9adc 100644
> --- a/Documentation/git-check-ref-format.txt
> +++ b/Documentation/git-check-ref-format.txt
> @@ -52,6 +52,8 @@ Git imposes the following rules on how references are named:
>
>  . They cannot end with a dot `.`.
>
> +. They cannot be the single character `@`.
> +
>  . They cannot contain a sequence `@{`.
>
>  . They cannot contain a `\`.
> diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
> index d477b3f..9b2e653 100644
> --- a/Documentation/revisions.txt
> +++ b/Documentation/revisions.txt
> @@ -27,6 +27,10 @@ blobs contained in a commit.
>    When ambiguous, a '<refname>' is disambiguated by taking the
>    first match in the following rules:
>
> +  . '@' is a special pseudo-ref that refers to HEAD.