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