Use one run_safe for `feature merge`.

This allows run_safe to print *all* commands that would have run if the
merge was successful.
Remove commented out code.

Why keep the cruft? It's not being used for anything.
Merge use-one-run-safe-for-feature-merge (#83) into master

Use one run_safe for `feature merge`.

This allows run_safe to print *all* commands that would have run if the
merge was successful.