Fix -Wuninitialized warning

src/blob.c

@@ -68,7 +68,7 @@ static int write_file_stream(
 	int fd, error;
 	char buffer[4096];
 	git_odb_stream *stream = NULL;
-	ssize_t read_len, written = 0;
+	ssize_t read_len = -1, written = 0;
 
 	if ((error = git_odb_open_wstream(
 			&stream, odb, (size_t)file_size, GIT_OBJ_BLOB)) < 0)

src/odb.c

@@ -115,7 +115,7 @@ int git_odb__hashfd(git_oid *out, git_file fd, size_t size, git_otype type)
 	int hdr_len;
 	char hdr[64], buffer[2048];
 	git_hash_ctx *ctx;
-	ssize_t read_len;
+	ssize_t read_len = -1;
 
 	hdr_len = format_object_header(hdr, sizeof(hdr), size, type);