Merge branch 'pw/rebase-reflog-fixes'

Merge branch 'pw/rebase-reflog-fixes'

Fix some bugs in the reflog messages when rebasing and changes the
reflog messages of "rebase --apply" to match "rebase --merge" with
the aim of making the reflog easier to parse.

* pw/rebase-reflog-fixes:
  rebase: cleanup action handling
  rebase --abort: improve reflog message
  rebase --apply: make reflog messages match rebase --merge
  rebase --apply: respect GIT_REFLOG_ACTION
  rebase --merge: fix reflog message after skipping
  rebase --merge: fix reflog when continuing
  t3406: rework rebase reflog tests
  rebase --apply: remove duplicated code