replace memset with string-list initializers

Using memset and then manually setting values of the string-list
members is not future proof as the internal representation of
string-list may change any time.
Use `string_list_init()` or STRING_LIST_INIT_* macros instead of
memset.

Signed-off-by: Tanay Abhra <tanayabh@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -423,8 +423,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix,
 			die(_("cannot do a partial commit during a cherry-pick."));
 	}
 
-	memset(&partial, 0, sizeof(partial));
-	partial.strdup_strings = 1;
+	string_list_init(&partial, 1);
 	if (list_paths(&partial, !current_head ? NULL : "HEAD", prefix, &pathspec))
 		exit(1);
 

merge-recursive.c

@@ -2062,12 +2062,9 @@ void init_merge_options(struct merge_options *o)
 	if (o->verbosity >= 5)
 		o->buffer_output = 0;
 	strbuf_init(&o->obuf, 0);
-	memset(&o->current_file_set, 0, sizeof(struct string_list));
-	o->current_file_set.strdup_strings = 1;
-	memset(&o->current_directory_set, 0, sizeof(struct string_list));
-	o->current_directory_set.strdup_strings = 1;
-	memset(&o->df_conflict_file_set, 0, sizeof(struct string_list));
-	o->df_conflict_file_set.strdup_strings = 1;
+	string_list_init(&o->current_file_set, 1);
+	string_list_init(&o->current_directory_set, 1);
+	string_list_init(&o->df_conflict_file_set, 1);
 }
 
 int parse_merge_opt(struct merge_options *o, const char *s)

submodule.c

@@ -544,10 +544,7 @@ static int push_submodule(const char *path)
 int push_unpushed_submodules(unsigned char new_sha1[20], const char *remotes_name)
 {
 	int i, ret = 1;
-	struct string_list needs_pushing;
-
-	memset(&needs_pushing, 0, sizeof(struct string_list));
-	needs_pushing.strdup_strings = 1;
+	struct string_list needs_pushing = STRING_LIST_INIT_DUP;
 
 	if (!find_unpushed_submodules(new_sha1, remotes_name, &needs_pushing))
 		return 1;

transport.c

@@ -1188,10 +1188,8 @@ int transport_push(struct transport *transport,
 		if ((flags & (TRANSPORT_RECURSE_SUBMODULES_ON_DEMAND |
 			      TRANSPORT_RECURSE_SUBMODULES_CHECK)) && !is_bare_repository()) {
 			struct ref *ref = remote_refs;
-			struct string_list needs_pushing;
+			struct string_list needs_pushing = STRING_LIST_INIT_DUP;
 
-			memset(&needs_pushing, 0, sizeof(struct string_list));
-			needs_pushing.strdup_strings = 1;
 			for (; ref; ref = ref->next)
 				if (!is_null_sha1(ref->new_sha1) &&
 				    find_unpushed_submodules(ref->new_sha1,