Merge branches 'sb/commit-tree-minileak', 'pm/log-exit-code', 'ml/submodule-foreach...

Merge branches 'sb/commit-tree-minileak', 'pm/log-exit-code', 'ml/submodule-foreach' and 'pb/reflog-dwim' into next

* sb/commit-tree-minileak:
  Fix commit_tree() buffer leak

* pm/log-exit-code:
  Teach git log --exit-code to return an appropriate exit code
  Teach git log --check to return an appropriate exit code

* ml/submodule-foreach:
  git-submodule - Add 'foreach' subcommand

* pb/reflog-dwim:
  builtin-reflog: Allow reflog expire to name partial ref