Merge branch 'sp/reflog' into next

* sp/reflog:
  Enable ref log creation in git checkout -b.
  Create/delete branch ref logs.
  Include ref log detail in commit, reset, etc.
  Change order of -m option to update-ref.
  Correct force_write bug in refs.c
  Change 'master@noon' syntax to 'master@{noon}'.
  Log ref updates made by fetch.
  Force writing ref if it doesn't exist.
  Added logs/ directory to repository layout.
  General ref log reading improvements.
  Fix ref log parsing so it works properly.
  Support 'master@2 hours ago' syntax
  Log ref updates to logs/refs/<ref>
  Convert update-ref to use ref_lock API.
  Improve abstraction of ref lock/write.

git-am.sh

@@ -413,7 +413,7 @@ do
 	parent=$(git-rev-parse --verify HEAD) &&
 	commit=$(git-commit-tree $tree -p $parent <"$dotest/final-commit") &&
 	echo Committed: $commit &&
-	git-update-ref HEAD $commit $parent ||
+	git-update-ref -m "am: $SUBJECT" HEAD $commit $parent ||
 	stop_here $this
 
 	if test -x "$GIT_DIR"/hooks/post-applypatch