Merge branch 'tb/ls-refs-optim'

The ls-refs protocol operation has been optimized to narrow the
sub-hierarchy of refs/ it walks to produce response.

* tb/ls-refs-optim:
  ls-refs.c: traverse prefixes of disjoint "ref-prefix" sets
  ls-refs.c: initialize 'prefixes' before using it
  refs: expose 'for_each_fullref_in_prefixes'

refs.h

@@ -347,6 +347,15 @@ int refs_for_each_fullref_in(struct ref_store *refs, const char *prefix,
 int for_each_fullref_in(const char *prefix, each_ref_fn fn, void *cb_data,
 			unsigned int broken);
 
+/**
+ * iterate all refs in "patterns" by partitioning patterns into disjoint sets
+ * and iterating the longest-common prefix of each set.
+ *
+ * callers should be prepared to ignore references that they did not ask for.
+ */
+int for_each_fullref_in_prefixes(const char *namespace, const char **patterns,
+				 each_ref_fn fn, void *cb_data,
+				 unsigned int broken);
 /**
  * iterate refs from the respective area.
  */