Ruby lint. Sorta.
https://github.com/kevinclark/nitpick/wikis
Clio:nitpick kev$ ./bin/nitpick spec/fixtures/block_badness.rb \
>     spec/fixtures/branch_badness.rb \
>     spec/fixtures/method_badness.rb \
>     spec/fixtures/rescue_badness.rb \
>     spec/fixtures/local_variable_badness.rb
./spec/fixtures/branch_badness.rb:20: warning: found = in conditional, should be ==
Fixtures::BlockBadness
  no_conditional_for_block_given
    - A block is being yielded to without a check for block_given?
  simple_conditional_without_check
    - A block is being yielded to without a check for block_given?
Fixtures::BranchBadness
  branch_returning_identical_things
    - The branches of 'if (true)' are identical.
  branch_returning_true_or_false
    - No need for an if. Just return '(1 == 2)' as a boolean.
  branch_with_assignment_as_condition
    - An assigment is being used as a condition: (a = 1)
    - The variable :a is unused.
Fixtures::LocalVariableBadness
  anonymous_args
    - The method :anonymous_args is empty.
  block_arg_unused
    - The argument :block is unused.
  lvar_shadowed
    - One or more variables are being shadowed (x)
  lvar_shadowed_many_block_vars
    - One or more variables are being shadowed (x)
  rescue_to_variable
    - The variable :e is unused.
  simple_unused_arg
    - The argument :other is unused.
  unused_arg
    - The argument :arg is unused.
  unused_lasgn
    - The variable :bar is unused.
Fixtures::MethodBadness
  empty_method
    - The method :empty_method is empty.
Fixtures::RescueBadness
  rescue_exception
    - A rescue is capturing Object or Exception, which may hide errors.
  rescue_nil
    - A rescue is returning "nil" directly and may not handle an error.
  rescue_object
    - A rescue is capturing Object or Exception, which may hide errors.