Side-by-side comparison of components

[gregelin]

Is your feature request related to a problem? Please describe.
When I notice two similarly named components in the component library with identical (or similar) statement counts, I worry if one component is actually a copy of the other component. It's a problem to open the components in different browser windows and manually compare the components statement by statement especially if there are dozens of control statements.

Describe the solution you'd like
I'd like a way to compare components in the component library similar to comparing products on a shopping site. I'd like to be select a two (or maybe more) components in a search results and have the components be displayed side-by-side so I can glance and see what's different.

Even better, I'd like to only see the differences or be able to choose to only see differences. I want the computer to do the work of comparing the components and showing me if a control exists in one but not in the other, or if the both components have component implementation statements that differ for the same control. I probably don't need to see if the controls where the statements are identical for both.

Describe alternatives you've considered

• I've considered doing a search and the search results have a check box for each found component so I can choose several components to display side by side.
• I've considered the idea of two columns and being able to choose from a drop down in each column what component to display
• I've considered an interface like GitHub where you there are two drop select boxes. You choose a component in each and then a page is loaded with the comparison

Additional context
There's an algorithm in the code that is used to compare to text strings for difference that is used on the three-column control statement editing page to show the differences between component's "certified" (or prototype) statement and the statement that exists for the system.

IMPORTANT: There's a new controls.Element.consuming_systems in #1618

[gregelin]

Initial implementation does not need to be side-by-side. Can be vertical.