remote/client: add write-image-like write-file command

[a3f]

Description

• what do you use the feature for?

Interactive use with labgrid-client. It's useful for bootloader development for processors with bootroms that load code from file systems (e.g. EFI system partition, OMAP, AT91, Zynq, Raspberry ... etc.)

• how does labgrid benefit as a testing library from the feature?

I guess a unit test could place e.g. a broken configuration file and see how it behaves?

• how did you verify the feature works?

Remote usbsdmux that I usually use with write-image. Tried writing non-existing files and overwriting existing files with write-file. Works well.

• if hardware is needed for the feature, which hardware is supported and which hardware did you test with?

Anything exposing a USBStorageDriver. I tested with a usbsdmux.

Checklist

• [x] Documentation for the feature
• [-] Tests for the feature
• [x] The arguments and description in doc/configuration.rst have been updated
• [-] Add a section on how to use the feature to doc/usage.rst
• [-] Add a section on how to use the feature to doc/development.rst
• [x] CHANGES.rst has been updated
• [x] PR has been tested
• [x] Man pages have been regenerated

[Emantor]

#548

[Emantor]

Closing this, please add udisks2 support instead of pmount and open a new PR.