Function svn_config_set 

pub unsafe extern "C" fn svn_config_set(
    cfg: *mut svn_config_t,
    section: *const c_char,
    option: *const c_char,
    value: *const c_char,
)

Add or replace the value of a (@a section, @a option) pair in @a cfg with @a value.

This function invalidates all value expansions in @a cfg.

To remove an option, pass NULL for the @a value.