Merge branch 'gr/rebase-i-drop-warn' into maint

"git rebase -i" had a minor regression recently, which stopped
considering a line that begins with an indented '#' in its insn
sheet not a comment, which is now fixed.

* gr/rebase-i-drop-warn:
rebase-i: loosen over-eager check_bad_cmd check
rebase-i: explicitly accept tab as separator in commands

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

diff --cc t/t3404-rebase-interactive.sh
Simple merge