I kind of wish there was a shell that had the option for histories localized to a directory. So I can go into a directory and then look at what I was doing when I was last in that directory. Some complicated compilation command line to compile and link a source file and a bunch of libraries that was run when I was last in that directory, for example. There'd still be the 'history' command for everything and then maybe 'dhistory' for the commands that I ran in that specific directory when I was last there.
I've never seen a mid-sized C codebase that annotate "restrict", "nonnull" pointers and "pure", "const" functions so thoroughly, very interesting, would be an important case study if I ever get around to write C optimizer passes.