Merge branch 'hn/refs-trace-backend'

Developer support.

* hn/refs-trace-backend:
  refs: add GIT_TRACE_REFS debugging mechanism

Author: gitster

Documentation/git.txt

@@ -722,6 +722,10 @@ of clones and fetches.
 	time of each Git command.
 	See `GIT_TRACE` for available trace output options.
 
+`GIT_TRACE_REFS`::
+	Enables trace messages for operations on the ref database.
+	See `GIT_TRACE` for available trace output options.
+
 `GIT_TRACE_SETUP`::
 	Enables trace messages printing the .git, working tree and current
 	working directory after Git has completed its setup phase.

Makefile

@@ -955,6 +955,7 @@ LIB_OBJS += rebase.o
 LIB_OBJS += ref-filter.o
 LIB_OBJS += reflog-walk.o
 LIB_OBJS += refs.o
+LIB_OBJS += refs/debug.o
 LIB_OBJS += refs/files-backend.o
 LIB_OBJS += refs/iterator.o
 LIB_OBJS += refs/packed-backend.o

refs.c

@@ -1774,6 +1774,7 @@ struct ref_store *get_main_ref_store(struct repository *r)
 		BUG("attempting to get main_ref_store outside of repository");
 
 	r->refs_private = ref_store_init(r->gitdir, REF_STORE_ALL_CAPS);
+	r->refs_private = maybe_debug_wrap_ref_store(r->gitdir, r->refs_private);
 	return r->refs_private;
 }