Merge branch 'jp/get-ref-dir-unsorted'

* jp/get-ref-dir-unsorted:
  refs.c: free duplicate entries in the ref array instead of leaking them
  refs.c: abort ref search if ref array is empty
  refs.c: ensure struct whose member may be passed to realloc is initialized
  refs: Use binary search to lookup refs faster
  Don't sort ref_list too early

Conflicts:
	refs.c

refs.h

@@ -57,7 +57,7 @@ extern void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refn
  */
 extern void add_extra_ref(const char *refname, const unsigned char *sha1, int flags);
 extern void clear_extra_refs(void);
-extern int ref_exists(char *);
+extern int ref_exists(const char *);
 
 extern int peel_ref(const char *, unsigned char *);