Re: [PATCH v2 5/6] Add new @ shortcut for HEAD

> 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'.
>
> So now we can use 'git show @~1', and all that goody goodness.
>
> Until now '@' was a valid name, but it conflicts with this idea, so lets
> make it invalid. Very few people if any probably used this name, if they
> did, they can rename it by using the full-path (e.g. refs/heads/@).
>
> Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
> ---
>  Documentation/git-check-ref-format.txt | 2 ++
>  Documentation/revisions.txt            | 3 +++
>  refs.c                                 | 4 ++++
>  sha1_name.c                            | 6 +++++-
>  t/t1508-at-combinations.sh             | 3 +++
>  5 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/git-check-ref-format.txt b/Documentation/git-check-ref-format.txt
> index ec1739a..e8035ec 100644
> --- a/Documentation/git-check-ref-format.txt
> +++ b/Documentation/git-check-ref-format.txt
> @@ -54,6 +54,8 @@ Git imposes the following rules on how references are named:
>  
>  . They cannot contain a sequence `@{`.
>  
> +. They cannot be the single character `@`.
> +
>  . They cannot contain a `\`.
>  
>  These rules make it easy for shell script based tools to parse
> diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
> index d477b3f..09896a3 100644
> --- a/Documentation/revisions.txt
> +++ b/Documentation/revisions.txt
> @@ -58,6 +58,9 @@ the '$GIT_DIR/refs' directory or from the '$GIT_DIR/packed-refs' file.
>  While the ref name encoding is unspecified, UTF-8 is preferred as
>  some output processing may assume ref names in UTF-8.
>  
> +'@'::
> +  '@' alone is a shortcut for 'HEAD'.
> +
>  '<refname>@\{<date>\}', e.g. 'master@\{yesterday\}', 'HEAD@\{5 minutes ago\}'::
>    A ref followed by the suffix '@' with a date specification
>    enclosed in a brace
> diff --git a/refs.c b/refs.c
> index de2d8eb..4e70b3e 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -72,6 +72,10 @@ int check_refname_format(const char *refname, int flags)
>  {
>  	int component_len, component_count = 0;
>  
> +	if (!strcmp(refname, "@"))
> +		/* Refname is a single character '@'. */
> +		return -1;