This commit adds a cache for Git repositories based on the path being queried.
Its only immediate effect is that when you query the same directory twice (such as /testcases/git /testcases/git), it won’t need to check that the second one is a Git directory the second time. So, a minuscule optimisation for something you’d never do anyway? Wrong! It’s going to let us combine multiple entries over the same repository later, letting us use --tree and --recurse, because now Git scanning is behind a factory.
I want to be very careful when doing the “--git and --tree don’t work together” one to not search for more Git repositories than I should. Being able to log when a repository is looked up and also switch that functionality on and off would help with that.
This commit moves file, dir, and the feature modules into one parent 'fs' module. Now there are three main 'areas' of the code: main and options, the filesystem-touching code, and the output-displaying code.
It should be the case that nothing in 'output' touches 'std::fs'.
