Re: [PATCH 3/3] gitweb: Link to "git describe"'d commits in log messages

[Junio C Hamano <gitster@pobox.com>]

Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:

> There's surely room for improvement here, but I just wanted to address
> the very common case of sticking "git describe" output into commit
> messages without trying to link to all possible refnames, that's going
> to be a rather futile exercise given that this is free text, and it
> would be prohibitively expensive to look up whether the references in
> question exist in our repository.

When I saw 2/3 I wondered about one thing and 3/3 shares the same,
which is that we only use regex match and do not validate for a
false match.  Would it be too expensive to pick up what _looks_ like
a rev (e.g. hex or g(refname regexp)-hex) then validate it with
"rev-parse --verify --quiet" to make sure it is a rev, before
actually making it a link?  Even if are we trying to account for
people referring to commits that do not exist in this repository
(e.g. some other project, in a submodule repository, or just an
earlier incarnation of rebasing that has since been lost), it seems
to me that it does not help to mark them with a link that won't
resolve.

> ---
>  gitweb/gitweb.perl | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
> index 101dbc0..3a52bc7 100755
> --- a/gitweb/gitweb.perl
> +++ b/gitweb/gitweb.perl
> @@ -2036,10 +2036,24 @@ sub format_log_line_html {
>  	my $line = shift;
>  
>  	$line = esc_html($line, -nbsp=>1);
> -	$line =~ s{\b([0-9a-fA-F]{7,40})\b}{
> +	$line =~ s{
> +        \b
> +        (
> +            # The output of "git describe", e.g. v2.10.0-297-gf6727b0
> +            # or hadoop-20160921-113441-20-g094fb7d
> +            (?<!-) # see strbuf_check_tag_ref(). Tags can't start with -
> +            [A-Za-z0-9.-]+
> +            (?!\.) # refs can't end with ".", see check_refname_format()
> +            -g[0-9a-fA-F]{7,40}
> +            |
> +            # Just a normal looking Git SHA1
> +            [0-9a-fA-F]{7,40}
> +        )
> +        \b
> +    }{
>  		$cgi->a({-href => href(action=>"object", hash=>$1),
>  					-class => "text"}, $1);
> -	}eg;
> +	}egx;
>  
>  	return $line;
>  }