Merge branch 'jc/stash-drop'

"git stash drop" is reimplemented as an internal call to
reflog_delete() function, instead of invoking "git reflog delete"
via run_command() API.

* jc/stash-drop:
  stash: call reflog_delete() in reflog.c
  reflog: libify delete reflog function and helpers
  stash: add tests to ensure reflog --rewrite --updatref behavior

Author: gitster

Makefile

@@ -1013,6 +1013,7 @@ LIB_OBJS += rebase-interactive.o
 LIB_OBJS += rebase.o
 LIB_OBJS += ref-filter.o
 LIB_OBJS += reflog-walk.o
+LIB_OBJS += reflog.o
 LIB_OBJS += refs.o
 LIB_OBJS += refs/debug.o
 LIB_OBJS += refs/files-backend.o