For my team, the solution has been writing longer commit messages detailing not only what has changed, but also the why and other considerations, potential pitfalls and so forth.

So in this case, a good commit message might read like:

``` Created square root approximation function

This is needed for rendering new polygons in renderer Foo in an efficient way as those don't need high degree of accuracy.

The algorithm used was Newton-Raphson approximation, accuracy was chosen by initial testing:

[[Test code here showing why a thing was chosen]]

Potential pitfalls here include foo and bar. X and Y were also considered, but left out due to unclear benefit over the simpler algorithm. ```

With an editor with good `git blame` support (or using github to dig through the layers) this gives me a lot of confidence about reading code as I can go back in time and read what the author was thinking about originally. This way I can evaluate properly if conditions have changed, rather than worry about the next Chthulu comment that does not apply.

Then you can have them duke it out running identical unit tests in the profiler.

That creates a clean separation between the people who just need to know what a function does and those that need to know how that function works. People who just need an approximated square root fast can understand perfectly well what ISquareRootApproximator.ApproximateSquareRoot( r ) does, and don't necessarily care whether your "get me a square root approximator" function returns a NewtonRaphsonAlgorithm, or a CORDICAlgorithm, or a BitshiftsMagicNumbersAndLookupTablesAlgorithm, or something else, so long as it approximates a square root.