Allow setting export path as a parameter

[moltar]

Currently running an export command requires a redirect:

dokku redis:export lolipop > lolipop.rdb

However, when running the command via SSH, it is not possible to redirect to the host server, and instead the export just dumbs into the SSH session.

ssh dokku@host "redis:export lolipop > lolipop.rdb"

Will export the data to STDOUT.

Ideally, a parameter should be added (e.g. -f --file) that will take the destination file path to dump the exported data to.

This feature is highly desired and essential for the following use cases:

• custom backup strategies triggered from another server
• CI and deployment tools that need to create a dump/backup before a release

Thank you!