Subject: Re: [PATCH v3 3/6] revision: introduce struct to handle exclusions

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Mon, 07 Nov 2022 13:51:51 +0100

On Mon, Nov 07 2022, Patrick Steinhardt wrote:

> [[PGP Signed Part:Undecided]]
> The functions that handle exclusion of refs work on a single string
> list. We're about to add a second mechanism for excluding refs though,
> and it makes sense to reuse much of the same architecture for both kinds
> of exclusion.
>
> Introduce a new `struct ref_exclusions` that encapsulates all the logic
> related to excluding refs.

I think it's a good change, but probably worth mentioning tha we're
moving the "excluded_refs" from being malloc'd to the "struct
string_list" being embedded in this new "struct ref_exclusions".

That change isn't necessary for hoisting it into a container struct, but
does make things nicer down the line.

>  	struct string_list_item *item;
> -
> -	if (!ref_excludes)
> -		return 0;
> -	for_each_string_list_item(item, ref_excludes) {
> +	for_each_string_list_item(item, &exclusions->excluded_refs) {
>  		if (!wildmatch(item->string, path, 0))
>  			return 1;

E.g. because here we don't care about the distinction between NULL and
!list->nr anymore, it *does* matter in some cases, but it's always nice
to be able to clearly distinguish the cases where we don't, such as this
one....

> -void clear_ref_exclusion(struct string_list **ref_excludes_p)
> +void init_ref_exclusions(struct ref_exclusions *exclusions)
>  {
> -	if (*ref_excludes_p) {
> -		string_list_clear(*ref_excludes_p, 0);
> -		free(*ref_excludes_p);
> -	}
> -	*ref_excludes_p = NULL;

...and this becomes much nicer.

Aside: There's some churn, and this diff is worse for the
rename-while-at-it of "clear_ref_exclusion" to "add_ref_exclusion", but
that's probably worth it to have the macro match the struct name etc.

> +	string_list_init_dup(&exclusions->excluded_refs);

Okey, so this is partly my fault for not following up on f196c1e908d
(revisions API users: use release_revisions() needing REV_INFO_INIT,
2022-04-13) :); But here:

If we keep this *_init() function don't duplicate what you're adding to
the macro, just init this in terms of the macro. See the two-line
examples in:

	git grep -W memcpy.*blank

But here (and this is the part that's mostly me) as we don't malloc this
anymore you're only needing to keep this init function for
repo_init_revisions().

So, probably too big a digression for a "while at it", but FWIW this on
top of your topic would do:
	
	 revision.c | 10 ++--------
	 revision.h | 10 +++++++---
	 2 files changed, 9 insertions(+), 11 deletions(-)
	
	diff --git a/revision.c b/revision.c
	index 45652f9b0bb..cf352d1fa43 100644
	--- a/revision.c
	+++ b/revision.c
	@@ -1534,12 +1534,6 @@ int ref_excluded(const struct ref_exclusions *exclusions, const char *path)
	 	return 0;
	 }
	 
	-void init_ref_exclusions(struct ref_exclusions *exclusions)
	-{
	-	string_list_init_dup(&exclusions->excluded_refs);
	-	string_list_init_dup(&exclusions->hidden_refs);
	-}
	-
	 void clear_ref_exclusions(struct ref_exclusions *exclusions)
	 {
	 	string_list_clear(&exclusions->excluded_refs, 0);
	@@ -1897,7 +1891,8 @@ void repo_init_revisions(struct repository *r,
	 			 struct rev_info *revs,
	 			 const char *prefix)
	 {
	-	memset(revs, 0, sizeof(*revs));
	+	struct rev_info blank = REV_INFO_INIT;
	+	memcpy(revs, &blank, sizeof(*revs));
	 
	 	revs->repo = r;
	 	revs->abbrev = DEFAULT_ABBREV;
	@@ -1933,7 +1928,6 @@ void repo_init_revisions(struct repository *r,
	 
	 	init_display_notes(&revs->notes_opt);
	 	list_objects_filter_init(&revs->filter);
	-	init_ref_exclusions(&revs->ref_excludes);
	 }
	 
	 static void add_pending_commit_list(struct rev_info *revs,
	diff --git a/revision.h b/revision.h
	index fef5e063d16..75b8ecc307b 100644
	--- a/revision.h
	+++ b/revision.h
	@@ -94,6 +94,10 @@ struct ref_exclusions {
	 	 */
	 	struct string_list hidden_refs;
	 };
	+#define REF_EXCLUSIONS_INIT { \
	+	.excluded_refs = STRING_LIST_INIT_DUP, \
	+	.hidden_refs = STRING_LIST_INIT_DUP, \
	+}
	 
	 struct oidset;
	 struct topo_walk_info;
	@@ -371,7 +375,9 @@ struct rev_info {
	  * called before release_revisions() the "struct rev_info" can be left
	  * uninitialized.
	  */
	-#define REV_INFO_INIT { 0 }
	+#define REV_INFO_INIT { \
	+	.ref_excludes = REF_EXCLUSIONS_INIT, \
	+}
	 
	 /**
	  * Initialize a rev_info structure with default values. The third parameter may
	@@ -455,10 +461,8 @@ void show_object_with_name(FILE *, struct object *, const char *);
	 /**
	  * Helpers to check if a reference should be excluded.
	  */
	-#define REF_EXCLUSIONS_INIT { .excluded_refs = STRING_LIST_INIT_DUP, .hidden_refs = STRING_LIST_INIT_DUP }
	 
	 int ref_excluded(const struct ref_exclusions *exclusions, const char *path);
	-void init_ref_exclusions(struct ref_exclusions *);
	 void clear_ref_exclusions(struct ref_exclusions *);
	 void add_ref_exclusion(struct ref_exclusions *, const char *exclude);
	 void exclude_hidden_refs(struct ref_exclusions *, const char *section);

But I'll submit that cleanup seperately, but for now let's not duplicate
your REF_EXCLUSIONS_INIT macro here in init_ref_exclusions(), just have
the function do what the macro is doing, now that we don't need the
malloc.

> -void add_ref_exclusion(struct string_list **ref_excludes_p, const char *exclude)
> +void clear_ref_exclusions(struct ref_exclusions *exclusions)
>  {
> -	if (!*ref_excludes_p) {
> -		CALLOC_ARRAY(*ref_excludes_p, 1);
> -		(*ref_excludes_p)->strdup_strings = 1;
> -	}
> -	string_list_append(*ref_excludes_p, exclude);
> +	string_list_clear(&exclusions->excluded_refs, 0);

Also nicer.

>  static void add_pending_commit_list(struct rev_info *revs,
> @@ -2689,10 +2684,10 @@ static int handle_revision_pseudo_opt(struct rev_info *revs,
>  			init_all_refs_cb(&cb, revs, *flags);
>  			other_head_refs(handle_one_ref, &cb);
>  		}
> -		clear_ref_exclusion(&revs->ref_excludes);
> +		clear_ref_exclusions(&revs->ref_excludes);
>  	} else if (!strcmp(arg, "--branches")) {
>  		handle_refs(refs, revs, *flags, refs_for_each_branch_ref);
> -		clear_ref_exclusion(&revs->ref_excludes);
> +		clear_ref_exclusions(&revs->ref_excludes);
>  	} else if (!strcmp(arg, "--bisect")) {
>  		read_bisect_terms(&term_bad, &term_good);
>  		handle_refs(refs, revs, *flags, for_each_bad_bisect_ref);
> @@ -2701,15 +2696,15 @@ static int handle_revision_pseudo_opt(struct rev_info *revs,
>  		revs->bisect = 1;
>  	} else if (!strcmp(arg, "--tags")) {
>  		handle_refs(refs, revs, *flags, refs_for_each_tag_ref);
> -		clear_ref_exclusion(&revs->ref_excludes);
> +		clear_ref_exclusions(&revs->ref_excludes);
>  	} else if (!strcmp(arg, "--remotes")) {
>  		handle_refs(refs, revs, *flags, refs_for_each_remote_ref);
> -		clear_ref_exclusion(&revs->ref_excludes);
> +		clear_ref_exclusions(&revs->ref_excludes);
>  	} else if ((argcount = parse_long_opt("glob", argv, &optarg))) {
>  		struct all_refs_cb cb;
>  		init_all_refs_cb(&cb, revs, *flags);
>  		for_each_glob_ref(handle_one_ref, optarg, &cb);
> -		clear_ref_exclusion(&revs->ref_excludes);
> +		clear_ref_exclusions(&revs->ref_excludes);
>  		return argcount;
>  	} else if ((argcount = parse_long_opt("exclude", argv, &optarg))) {
>  		add_ref_exclusion(&revs->ref_excludes, optarg);
> @@ -2718,17 +2713,17 @@ static int handle_revision_pseudo_opt(struct rev_info *revs,
>  		struct all_refs_cb cb;
>  		init_all_refs_cb(&cb, revs, *flags);
>  		for_each_glob_ref_in(handle_one_ref, optarg, "refs/heads/", &cb);
> -		clear_ref_exclusion(&revs->ref_excludes);
> +		clear_ref_exclusions(&revs->ref_excludes);
>  	} else if (skip_prefix(arg, "--tags=", &optarg)) {
>  		struct all_refs_cb cb;
>  		init_all_refs_cb(&cb, revs, *flags);
>  		for_each_glob_ref_in(handle_one_ref, optarg, "refs/tags/", &cb);
> -		clear_ref_exclusion(&revs->ref_excludes);
> +		clear_ref_exclusions(&revs->ref_excludes);
>  	} else if (skip_prefix(arg, "--remotes=", &optarg)) {
>  		struct all_refs_cb cb;
>  		init_all_refs_cb(&cb, revs, *flags);
>  		for_each_glob_ref_in(handle_one_ref, optarg, "refs/remotes/", &cb);
> -		clear_ref_exclusion(&revs->ref_excludes);
> +		clear_ref_exclusions(&revs->ref_excludes);

The churn I mentioned with the renaming, so maybe worth doing that as a
"prep" commit?

> +struct ref_exclusions {
> +	/*
> +	 * Excluded refs is a list of wildmatch patterns. If any of the
> +	 * patterns matches, the reference will be excluded.
> +	 */
> +	struct string_list excluded_refs;
> +};

Per the above POC diff though, please move...

>  struct oidset;
>  struct topo_walk_info;
>  
> @@ -103,7 +111,7 @@ struct rev_info {
>  	struct list_objects_filter_options filter;
>  
>  	/* excluding from --branches, --refs, etc. expansion */
> -	struct string_list *ref_excludes;
> +	struct ref_exclusions ref_excludes;
>  
>  	/* Basic information */
>  	const char *prefix;
> @@ -439,12 +447,14 @@ void mark_trees_uninteresting_sparse(struct repository *r, struct oidset *trees)
>  void show_object_with_name(FILE *, struct object *, const char *);
>  
>  /**
> - * Helpers to check if a "struct string_list" item matches with
> - * wildmatch().
> + * Helpers to check if a reference should be excluded.
>   */
> -int ref_excluded(struct string_list *, const char *path);
> -void clear_ref_exclusion(struct string_list **);
> -void add_ref_exclusion(struct string_list **, const char *exclude);
> +#define REF_EXCLUSIONS_INIT { .excluded_refs = STRING_LIST_INIT_DUP }

...this macro to right after declaring the struct, which is what we
usually do, and will help in adding it to "REV_INFO_INIT" sooner than
later.

Also, at the end of your series this end up being overly long, so per
the diff-above (which is tot he end of the series), let's start by
line-wrapping it:

	#define ..._INIT { \
        	.member = ..._INIT, \
	}