Re: [RFC/PATCH] tag: add --points-at list option

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

Tom Grennan <tmgrennan@gmail.com> writes:

> @@ -105,16 +107,28 @@ static int show_reference(const char *refname, const unsigned char *sha1,
>  				return 0;
>  		}
>  
> +		buf = read_sha1_file(sha1, &type, &size);
> +		if (!buf || !size)
> +			return 0;
> +
> +		if (filter->points_at) {
> +			unsigned char tagged_sha1[20];
> +			if (memcmp("object ", buf, 7) \
> +			    || buf[47] != '\n' \
> +			    || get_sha1_hex(buf + 7, tagged_sha1) \
> +			    || memcmp(filter->points_at, tagged_sha1, 20)) {

Do we need these backslashes at the end of these lines?

> @@ -143,16 +157,20 @@ static int show_reference(const char *refname, const unsigned char *sha1,
>  }
>  
>  static int list_tags(const char **patterns, int lines,
> -			struct commit_list *with_commit)
> +			struct commit_list *with_commit,
> +			unsigned char *points_at)
>  {

It strikes me somewhat odd that you can give a list of commits to filter
when using "--contains" (e.g. "--contains v1.7.9 --contains 1.7.8.4"), but
you can only ask for a single object with "--points-at" from the UI point
of view.

> @@ -375,12 +393,28 @@ static int strbuf_check_tag_ref(struct strbuf *sb, const char *name)
>  	return check_refname_format(sb->buf, 0);
>  }
>  
> +int parse_opt_points_at(const struct option *opt, const char *arg, int unset)
> +{
> +	unsigned char *sha1;
> +
> +	if (!arg)
> +		return -1;
> +	sha1 = xmalloc(20);
> +	if (get_sha1(arg, sha1)) {
> +		free(sha1);
> +		return error("malformed object name %s", arg);
> +	}
> +	*(unsigned char **)opt->value = sha1;
> +	return 0;
> +}

We are ignoring earlier --points-at argument without telling the user that
we do not support more than one.

Would it become too much unnecessary addition of new code if you supported
multiple --points-at on the command line for the sake of consistency?

> @@ -417,6 +451,12 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>  			PARSE_OPT_LASTARG_DEFAULT,
>  			parse_opt_with_commit, (intptr_t)"HEAD",
>  		},
> +		{
> +			OPTION_CALLBACK, 0, "points-at", &points_at, "object",
> +			"print only annotated|signed tags of the object",
> +			PARSE_OPT_LASTARG_DEFAULT,
> +			parse_opt_points_at, (intptr_t)"HEAD",
> +		},

I wonder if defaulting to HEAD even makes sense for --points-at. When you
are chasing a bug and checked out an old version that originally had
problem, "git tag --contains" that defaults to HEAD does have a value. It
tells us what releases are potentially contaminated with the buggy commit.

But does a similar use case support points-at that defaults to HEAD?

Other than that, thanks for a pleasant read.