filter: introduce git_filter_list_apply_to_buffer

Provide a filter application mechanism that takes a user-provided string
and length, instead of a `git_buf`.

Author: ethomson

include/git2/filter.h

@@ -119,6 +119,21 @@ GIT_EXTERN(int) git_filter_list_contains(
 	git_filter_list *filters,
 	const char *name);
 
+/**
+ * Apply filter list to a data buffer.
+ *
+ * @param out Buffer to store the result of the filtering
+ * @param filters A loaded git_filter_list (or NULL)
+ * @param in Buffer containing the data to filter
+ * @param in_len The length of the input buffer
+ * @return 0 on success, an error code otherwise
+ */
+GIT_EXTERN(int) git_filter_list_apply_to_buffer(
+	git_buf *out,
+	git_filter_list *filters,
+	const char *in,
+	size_t in_len);
+
 /**
  * Apply filter list to a data buffer.
  *

src/filter.c

@@ -720,7 +720,7 @@ static void buf_stream_init(struct buf_stream *writer, git_buf *target)
 	git_buf_clear(target);
 }
 
-static int git_filter_list_apply_to_buffer(
+int git_filter_list_apply_to_buffer(
 	git_buf *out,
 	git_filter_list *filters,
 	const char *in,