[sdesol]

If you want to build a product with a build system, you need to tell it what source to include. With this information, you know what files to consider and if you are dealing with a statically typed language like C or C++, you have build artifacts that can tell you where the implementation was defined. All of this, takes the guess work out of answering questions like "What foo() implentation was used".

If all you know are repo branches, the best you can do is return matches from different repo branches with the hopes that one of them is right.

Edit: I should also add that with a build system, you know what version of a file to use.