in lib/pry/byebug/breakpoints.rb [62:73]
def add_file(file, line, expression = nil)
real_file = (file != Pry.eval_path)
raise(ArgumentError, "Invalid file!") if real_file && !File.exist?(file)
validate_expression expression
path = (real_file ? File.expand_path(file) : file)
bp = FileBreakpoint.new ::Byebug::Breakpoint.add(path, line, expression)
breakpoints << bp
bp
end