Specified parameters should overwrite loaded config files

[twalpole]

Fix issue #1199, #1200, #1201 by allowing specified parameters to overwrite those loaded from config files.

[pudiva]

this was already fixed on v3.6.2 and not merged on v3.7.0 for some reason.

[pudiva]

see #1200

[twalpole]

@ayghor It wasn't "fixed" on v3.6.2 - a fix for a different issue was reverted on 3.6.2 because while it fixed the previous issue it had created this new issue. So after reverting the previous issue still existed. This PR fixes both issues.

[pudiva]

oops sry for that <3

[twalpole]

@nateberkopec Thoughts?

[nateberkopec]

Wonderful, thanks @twalpole. Taking a look.

[bikramwp]

In Rails 5.0.1, this change looks like it causes the options in config/puma.rb to be ignored:

Scenario 1: config/puma.rb with custom bind option, running rails s command

config/puma.rb contains:

bind ENV.fetch("BIND") { "tcp://127.0.0.1:4444" }

In Puma 3.7.0, that generated an options array of:

[
  { ... , :Port=>3000, :Host=>"localhost"  },
  { ... , :binds=>["tcp://localhost:3000"] },
  { ... , :binds=>["tcp://127.0.0.1:4444"] }
]

In Puma 3.7.1, it generates:

[
  { ... , :binds=>["tcp://127.0.0.1:4444"] },
  { ... , :Port=>3000, :Host=>"localhost"  },
  { ... , :binds=>["tcp://localhost:3000"] }
]

Scenario 2: config/puma.rb with custom bind option, running rails s -p 9999 command

config/puma.rb: contains (same as Scenario 1):

bind ENV.fetch("BIND") { "tcp://127.0.0.1:4444" }

In Puma 3.7.0, that generated an options array of:

[
  { ... , :Port=>9999, :Host=>"localhost"  },
  { ... , :binds=>["tcp://localhost:9999"] },
  { ... , :binds=>["tcp://127.0.0.1:4444"] }
]

In Puma 3.7.1, it generates:

[
  { ... , :binds=>["tcp://127.0.0.1:4444"] },
  { ... , :Port=>9999, :Host=>"localhost"  },
  { ... , :binds=>["tcp://localhost:9999"] }
]

So, Rails' config (internal default or specified on rails s command) is always taking precedence
and config/puma.rb settings don't take effect.

I think this pull request is right in that rails s options should take priority over config/puma.rb,
but in the case where no rails s options are specified on the command line, config/puma.rb should
take precedence over Rails' internal defaults.

Unfortunately, I am not sure what the proper solution would be: is Rails configuring Puma incorrectly
or should Puma be working differently?

[nateberkopec]

@bikramwp see #1229.