The Bitrise CLI has a feature that allows for shell completion, which can be enabled using clever snippets or by modifying the configuration files of popular shells such as Bash and Zsh. These snippets or modifications allow users to automatically complete long workflow IDs in the terminal, making it easier to use the `bitrise run` command. The snippets are specific to each shell type and require different approaches, with Bash requiring a custom function `_bitrise()` that can be inserted into the shell's completion files, while Zsh uses a more complex approach involving a file called `_bitrise` in one of the directories listed in its configuration variable `$fpath`. Fish, on the other hand, has a simpler solution that involves copying a snippet into its configuration file.