Right now I can use include-files in my ~/.ssh/config which allow me to break the file up into more cohesive groupings. One thing about this, though, is that the actual config-file is just this include config.d/* which seems a bit redundant. Could you just check to see whether the ~/.ssh/config is a file or a directory, and if it's a directory, just use all the files in-order (which corresponds to what config.d/* does)?