ref-filter.h: provide `REF_FILTER_INIT`

Provide a sane initialization value for `struct ref_filter`, which in a
subsequent patch will be used to initialize a new field.

In the meantime, ensure that the `ref_filter` struct used in the
test-helper's `cmd__reach()` is zero-initialized. The lack of
initialization is OK, since `commit_contains()` only looks at the single
`with_commit_tag_algo` field that *is* initialized directly above.

So this does not fix a bug, but rather prevents one from biting us in
the future.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -707,7 +707,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	int reflog = 0, quiet = 0, icase = 0, force = 0,
 	    recurse_submodules_explicit = 0;
 	enum branch_track track;
-	struct ref_filter filter;
+	struct ref_filter filter = REF_FILTER_INIT;
 	static struct ref_sorting *sorting;
 	struct string_list sorting_options = STRING_LIST_INIT_DUP;
 	struct ref_format format = REF_FORMAT_INIT;
@@ -765,7 +765,6 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 
 	setup_ref_filter_porcelain_msg();
 
-	memset(&filter, 0, sizeof(filter));
 	filter.kind = FILTER_REFS_BRANCHES;
 	filter.abbrev = -1;
 

builtin/for-each-ref.c

@@ -24,7 +24,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	struct string_list sorting_options = STRING_LIST_INIT_DUP;
 	int maxcount = 0, icase = 0, omit_empty = 0;
 	struct ref_array array;
-	struct ref_filter filter;
+	struct ref_filter filter = REF_FILTER_INIT;
 	struct ref_format format = REF_FORMAT_INIT;
 	struct strbuf output = STRBUF_INIT;
 	struct strbuf err = STRBUF_INIT;
@@ -61,7 +61,6 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	};
 
 	memset(&array, 0, sizeof(array));
-	memset(&filter, 0, sizeof(filter));
 
 	format.format = "%(objectname) %(objecttype)\t%(refname)";
 

builtin/tag.c

@@ -443,7 +443,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	struct msg_arg msg = { .buf = STRBUF_INIT };
 	struct ref_transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
-	struct ref_filter filter;
+	struct ref_filter filter = REF_FILTER_INIT;
 	struct ref_sorting *sorting;
 	struct string_list sorting_options = STRING_LIST_INIT_DUP;
 	struct ref_format format = REF_FORMAT_INIT;
@@ -501,7 +501,6 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	git_config(git_tag_config, &sorting_options);
 
 	memset(&opt, 0, sizeof(opt));
-	memset(&filter, 0, sizeof(filter));
 	filter.lines = -1;
 	opt.sign = -1;
 

ref-filter.h

@@ -92,6 +92,9 @@ struct ref_format {
 	struct string_list bases;
 };
 
+#define REF_FILTER_INIT { \
+	.points_at = OID_ARRAY_INIT, \
+}
 #define REF_FORMAT_INIT {             \
 	.use_color = -1,              \
 	.bases = STRING_LIST_INIT_DUP, \

t/helper/test-reach.c

@@ -139,7 +139,7 @@ int cmd__reach(int ac, const char **av)
 
 		printf("%s(X,_,_,0,0):%d\n", av[1], can_all_from_reach_with_flag(&X_obj, 2, 4, 0, 0));
 	} else if (!strcmp(av[1], "commit_contains")) {
-		struct ref_filter filter;
+		struct ref_filter filter = REF_FILTER_INIT;
 		struct contains_cache cache;
 		init_contains_cache(&cache);