reachable.hon commit git-compat-util.h: don't define _XOPEN_SOURCE on cygwin (3a0a3a8)
   1#ifndef REACHEABLE_H
   2#define REACHEABLE_H
   3
   4struct progress;
   5extern void mark_reachable_objects(struct rev_info *revs, int mark_reflog, struct progress *);
   6
   7#endif