Merge branch 'ab/plug-random-leaks'

Leakfix.

* ab/plug-random-leaks:
  reflog: free() ref given to us by dwim_log()
  submodule--helper: fix small memory leaks
  clone: fix a memory leak of the "git_dir" variable
  grep: fix a "path_list" memory leak
  grep: use object_array_clear() in cmd_grep()
  grep: prefer "struct grep_opt" over its "void *" equivalent