Merge branch 'sg/rebase-progress'

Merge branch 'sg/rebase-progress'

Use "Erase in Line" CSI sequence that is already used in the editor
support to clear cruft in the progress output.

* sg/rebase-progress:
  progress: use term_clear_line()
  rebase: fix garbled progress display with '-x'
  pager: add a helper function to clear the last line in the terminal
  t3404: make the 'rebase.missingCommitsCheck=ignore' test more focused
  t3404: modernize here doc style