Define merge strategy

[mattiaverga]

Add a strategy flag to decide how to auto-merge the PR:

• approve-and-merge will mimic actual default, approve the PR and comment with the merge command
• approve-only will only approve the PR, so that other automatic tools (such as mergify) can merge the PR when CI tests pass
• merge-only will mimic actual approve: false behavior, only post comment with the merge command without approving the PR

The default approve-and-merge will ensure backward compatibility with existent config files, however unexpected behavior will arise when using strategy: approve-and-merge together with approve: false, therefore when updating the config file the use of approve parameter is deprecated.

Fixes #176

Signed-off-by: Mattia Verga mattia.verga@tiscali.it

[eiskrenkov]

@mattiaverga wow, exactly what we need, thank you! @ahmadnassri great feature, will you consider to merge that?

[yeikel]

@ahmadnassri Sorry for the ping, but could you please review this?

[ahmadnassri]

apologies for the delay, been dealing with personal matters and have not looked at code in over a month...

confident I'll land this PR this week as part of a major rewrite