Remove dead code

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Trivial cleanup

$merged is an array of strings, no need to add an extra newline at the
end of each one.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Refactor code into Integration.start

Will be useful to reuse this code.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Trivial simplification

We don't need to store the full branch ref.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Add support for --apply

This option would be useful to apply pending branches to merge on top of
another (non-integration) branch. Mostly for comparison purposes.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Add missing help in the command line usage

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>