Commit
eff80a9 (Allow custom "comment char") introduced a custom comment
character for commit messages but did not teach git-rebase--interactive
to use it.
Change git-rebase--interactive to read core.commentchar and use its
value when generating commit messages and for the command list.
Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>