Improve interaction handler api

[robd]

This PR contains 4 improvements to the :interaction_handler option API from trying to use this with Capistrano in the real world:

1. Put the MappingInteractionHandler class in the SSHKit module
2. Support specifying an interaction_handler as a hash

# Before:
execute(:some_command, interaction_handler: SSHKit::MappingInteractionHandler.new("Some output\n" => "Input\n"))
# After:
execute(:some_command, interaction_handler: { "Some output\n" => "Input\n"})

3. No longer append a newline to the user input. This removes an inconsistency between the server side and user input side of the mapping:

# Before - newline needed on server output only because newline magically appended to input:
execute(:some_command, interaction_handler: { "Some output\n" => "Input"})
# After - no magic newline behaviour; all newlines should be specified:
execute(:some_command, interaction_handler: { "Some output\n" => "Input\n"})

4. Remove theoutput constructor parameter and attribute from MappingInteractionHandler. This was only added for unit testing purposes, but meant that it didn't work with airbrussh. It also meant that MappingInteractionHandler would hold on to a reference to SSHKit.config.output which seems a bit dodgy to me in the case that SSHKit.config.output is updated after the MappingInteractionHandler is created.

[leehambley]

Would a regex work here?

execute(:some_command, interaction_handler: { /Some output\n+/ => "Input\n"})

[robd]

@leehambley I have thought about adding support for this. At the moment, I simply treat the hash keys as hash keys so it won't work (I don't think, because hash uses eql? for key equality), but obviously I could add support for this.

Another option would be to support a lambda:

execute(:some_command, interaction_handler: lambda { |output_line|
  case output_line
  when /Some output\n+/
    "Input\n"
  end
)

I definitely think that some way to match a regex would be helpful. This { /Some output\n+/ => "Input\n"} feels a bit non idiomatic, but is much nicer for one liners.

[robd]

I also added a fix (e93f819) for a change of behaviour I accidentally introduced to do with mutating strings which broke airbrussh in a non obvious way and forced @mattbrictson to implement a pretty nasty workaround.

[leehambley]

Oopse sorry @mattbrictson :) I missed the link with airbrussh when reviewing this :(

[robd]

@leehambley I'm adding regex support now. Will update this PR soon.

[robd]

@leehambley OK, I now compare the hash keys using case equality to support regexes. I also support specifying a proc. I also changed the behaviour for unmapped commands to output at the debug level instead of warning level.

Both now supported:

execute(:some_command, interaction_handler: { /Some output\n+/ => "Input\n"})

# OR

execute(:some_command, interaction_handler: lambda { |output_line|
  case output_line
  when /Some output\n+/
    "Input\n"
  end
)

One thing to note is that since the on_stdout/on_stderr are called once per stdout/stderr line, I think that \n+ in your regex won't ever get a chance to match multiple newlines.

[mattbrictson]

@robd Thanks! I tested this branch and it fixes the issue that required me to add the deep_copy workaround to airbrussh.

[robd]

@mattbrictson OK great - thanks vm for checking

[leehambley]

At first glance (can't review too thoroughly, or try your branch out) but this all looks sane, with such a flexible API making the docs clean and clear will be essential.

[leehambley]

Happy to merge, if you are ?

[robd]

@leehambley Yes, I'm happy with this - thanks. I hope the Readme covers all usage patterns, but if anything crops up I will raise as a separate PR.