Function svn_path_add_component 

pub unsafe extern "C" fn svn_path_add_component(
    path: *mut svn_stringbuf_t,
    component: *const c_char,
)

Add a @a component (a NULL-terminated C-string) to the canonicalized @a path. @a component is allowed to contain directory separators.

If @a path is non-empty, append the appropriate directory separator character, and then @a component. If @a path is empty, simply set it to @a component; don’t add any separator character.

If the result ends in a separator character, then remove the separator.