Check if string is prefix of stralloc
#include <stralloc.h>
int stralloc_starts(stralloc* sa,const char* in);
stralloc_starts returns 1 if the \0-terminated string in in, without the terminating \0, is a prefix of the string stored in sa. Otherwise it returns 0. sa must already be allocated.
1 if in is a prefix of sa, otherwise 0.
str_starts(3)