Re: [PATCH 1/2] pathspec: allow querying for attributes

[Jonathan Tan <jonathantanmy@google.com>]

On 03/09/2017 01:07 PM, Brandon Williams wrote:
> diff --git a/Documentation/glossary-content.txt b/Documentation/glossary-content.txt
> index fc9320e59..5c32d1905 100644
> --- a/Documentation/glossary-content.txt
> +++ b/Documentation/glossary-content.txt
> @@ -384,6 +384,26 @@ full pathname may have special meaning:
>  +
>  Glob magic is incompatible with literal magic.
>
> +attr;;
> +After `attr:` comes a space separated list of "attribute
> +requirements", all of which must be met in order for the
> +path to be considered a match; this is in addition to the
> +usual non-magic pathspec pattern matching.
> ++
> +Each of the attribute requirements for the path takes one of
> +these forms:
> +
> +- "`ATTR`" requires that the attribute `ATTR` must be set.

As a relative newcomer to attributes, I was confused by the fact that 
"set" and "set to a value" is different (and likewise "unset" and 
"unspecified"). Maybe it's worthwhile including a link to 
"gitattributes" to explain the different (exclusive) states that an 
attribute can be in.

> +
> +- "`-ATTR`" requires that the attribute `ATTR` must be unset.
> +
> +- "`ATTR=VALUE`" requires that the attribute `ATTR` must be
> +  set to the string `VALUE`.
> +
> +- "`!ATTR`" requires that the attribute `ATTR` must be
> +  unspecified.

It would read better to me if you omitted "must" in all 4 bullet points 
(and it is redundant anyway with "requires"), but I don't feel too 
strongly about this.

> diff --git a/pathspec.c b/pathspec.c
> index b961f00c8..583ed5208 100644
> --- a/pathspec.c
> +++ b/pathspec.c
> @@ -87,6 +89,72 @@ static void prefix_magic(struct strbuf *sb, int prefixlen, unsigned magic)
>  	strbuf_addf(sb, ",prefix:%d)", prefixlen);
>  }
>
> +static void parse_pathspec_attr_match(struct pathspec_item *item, const char *value)
> +{
> +	struct string_list_item *si;
> +	struct string_list list = STRING_LIST_INIT_DUP;
> +
> +	if (item->attr_check)
> +		die(_("Only one 'attr:' specification is allowed."));
> +
> +	if (!value || !strlen(value))

You can write `!*value` instead of `!strlen(value)`.

> +		die(_("attr spec must not be empty"));
> +
> +	string_list_split(&list, value, ' ', -1);

You could avoid some allocations by using the in-place variant (since 
value is a newly allocated string not used elsewhere) but it is probably 
not that important in this argument parsing case.

> +	string_list_remove_empty_items(&list, 0);
> +
> +	item->attr_check = attr_check_alloc();
> +	ALLOC_GROW(item->attr_match,
> +		   item->attr_match_nr + list.nr,
> +		   item->attr_match_alloc);

Is there a time when this function is called while item->attr_match_nr 
is not zero?

> +
> +	for_each_string_list_item(si, &list) {
> +		size_t attr_len;
> +		char *attr_name;
> +		const struct git_attr *a;
> +
> +		int j = item->attr_match_nr++;
> +		const char *attr = si->string;
> +		struct attr_match *am = &item->attr_match[j];
> +
> +		switch (*attr) {
> +		case '!':
> +			am->match_mode = MATCH_UNSPECIFIED;
> +			attr++;
> +			attr_len = strlen(attr);
> +			break;
> +		case '-':
> +			am->match_mode = MATCH_UNSET;
> +			attr++;
> +			attr_len = strlen(attr);
> +			break;
> +		default:
> +			attr_len = strcspn(attr, "=");
> +			if (attr[attr_len] != '=')
> +				am->match_mode = MATCH_SET;
> +			else {
> +				am->match_mode = MATCH_VALUE;
> +				am->value = xstrdup(&attr[attr_len + 1]);
> +				if (strchr(am->value, '\\'))
> +					die(_("attr spec values must not contain backslashes"));
> +			}
> +			break;
> +		}
> +
> +		attr_name = xmemdupz(attr, attr_len);
> +		a = git_attr(attr_name);
> +		if (!a)
> +			die(_("invalid attribute name %s"), attr_name);
> +
> +		attr_check_append(item->attr_check, a);
> +
> +		free(attr_name);
> +	}
> +
> +	string_list_clear(&list, 0);
> +	return;

Redundant return?

> @@ -544,6 +628,10 @@ void parse_pathspec(struct pathspec *pathspec,
>  		if (item[i].nowildcard_len < item[i].len)
>  			pathspec->has_wildcard = 1;
>  		pathspec->magic |= item[i].magic;
> +
> +		if (item[i].attr_check &&
> +		    item[i].attr_check->nr != item[i].attr_match_nr)
> +			die("BUG: should have same number of entries");

I'm not sure if this check is giving us any benefit - I would expect 
this type of code before some other code that assumed that the numbers 
matched, and that will potentially segfault if not.