Merge branch 'pw/no-editor-in-rebase-i-implicit'

When GIT_SEQUENCE_EDITOR is set, the command was incorrectly
started when modes of "git rebase" that implicitly uses the
machinery for the interactive rebase are run, which has been
corrected.

* pw/no-editor-in-rebase-i-implicit:
  implicit interactive rebase: don't run sequence editor

diff --cc builtin/rebase.c
Simple merge

diff --cc git-legacy-rebase.sh
Simple merge