Merge branch 'pw/post-commit-from-sequencer'

Merge branch 'pw/post-commit-from-sequencer'

"rebase -i" ceased to run post-commit hook by mistake in an earlier
update, which has been corrected.

* pw/post-commit-from-sequencer:
  sequencer: run post-commit hook
  move run_commit_hook() to libgit and use it there
  sequencer.h fix placement of #endif
  t3404: remove uneeded calls to set_fake_editor
  t3404: set $EDITOR in subshell
  t3404: remove unnecessary subshell