Merge branch 'js/fix-merge-arg-quoting-in-rebase-p'

"git rebase -p -X<option>" did not propagate the option properly
down to underlying merge strategy backend.

* js/fix-merge-arg-quoting-in-rebase-p:
rebase -p: fix quoting when calling `git merge`

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