Function svn_io_write_version_file 

pub unsafe extern "C" fn svn_io_write_version_file(
    path: *const c_char,
    version: c_int,
    pool: *mut apr_pool_t,
) -> *mut svn_error_t

Create (or overwrite) the file at @a path with new contents, formatted as a non-negative integer @a version followed by a single newline. On successful completion the file will be read-only. Use @a pool for all allocations.