`ch-completion.bash` (PR #1618) uses lists of command line options, subcommands, etc. to generate completions. Currently, these lists are hard-coded into the script, meaning if the Charliecloud command line ever changes (which happens on a not-infrequent basis), the script needs to be manually updated. This presents a maintainability issue, as one could very easily forget to update the script when adding new CLI arguments. Furthermore, as the author of that script, I don't want to subject any of the other devs to reading it if such a thing can be avoided. We should consider changing these lists to auto-generate based on the `--help` outputs of the Charliecloud executables.