Adding git_filter_init for initializing `git_filter` struct + unit test

include/git2/sys/filter.h

@@ -272,6 +272,17 @@ struct git_filter {
 
 #define GIT_FILTER_VERSION 1
 #define GIT_FILTER_INIT {GIT_FILTER_VERSION}
+
+/**
+ * Initializes a `git_filter` with default values. Equivalent to
+ * creating an instance with GIT_FILTER_INIT.
+ *
+ * @param filter the `git_filter` struct to initialize.
+ * @param version Version the struct; pass `GIT_FILTER_VERSION`
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_filter_init(git_filter *filter, unsigned int version);
+
 /**
  * Register a filter under a given name with a given priority.
  *

src/filter.c

@@ -895,7 +895,7 @@ static int stream_list_init(
 			git_array_size(filters->filters) - 1 - i : i;
 		git_filter_entry *fe = git_array_get(filters->filters, filter_idx);
 		git_writestream *filter_stream;
-		
+
 		assert(fe->filter->stream || fe->filter->apply);
 
 		/* If necessary, create a stream that proxies the traditional
@@ -1022,3 +1022,9 @@ int git_filter_list_stream_blob(
 
 	return git_filter_list_stream_data(filters, &in, target);
 }
+
+int git_filter_init(git_filter *filter, unsigned int version)
+{
+	GIT_INIT_STRUCTURE_FROM_TEMPLATE(filter, version, git_filter, GIT_FILTER_INIT);
+	return 0;
+}

tests/core/structinit.c

 #include "clar_libgit2.h"
 #include <git2/sys/config.h>
+#include <git2/sys/filter.h>
 #include <git2/sys/odb_backend.h>
 #include <git2/sys/refdb_backend.h>
 #include <git2/sys/transport.h>
@@ -96,6 +97,11 @@ void test_core_structinit__compare(void)
 		git_diff_find_options, GIT_DIFF_FIND_OPTIONS_VERSION, \
 		GIT_DIFF_FIND_OPTIONS_INIT, git_diff_find_init_options);
 
+	/* filter */
+	CHECK_MACRO_FUNC_INIT_EQUAL( \
+		git_filter, GIT_FILTER_VERSION, \
+		GIT_FILTER_INIT, git_filter_init);
+
 	/* merge_file_input */
 	CHECK_MACRO_FUNC_INIT_EQUAL( \
 		git_merge_file_input, GIT_MERGE_FILE_INPUT_VERSION, \