void read_revisions_from_stdin(struct rev_info *revs);
typedef void (*show_early_output_fn_t)(struct rev_info *, struct commit_list *);
-volatile show_early_output_fn_t show_early_output;
+extern volatile show_early_output_fn_t show_early_output;
extern void init_revisions(struct rev_info *revs, const char *prefix);
extern int setup_revisions(int argc, const char **argv, struct rev_info *revs, const char *def);