FR: Bash Autocompletion

[jhedwardyang]

Tab should recommend and autocomplete for commands and options

[jhedwardyang]

bash and zsh provide tab-completion through bash scripts.

• git uses this (natively) through a (large) bash script.
• npm decided to use this a little differently, they have the bash script call npm again, but pass in a special flag. When the flag is seen, the code path will change to give recommendations (stdout). bash script. This script will print if you just type npm completion into a console
• omelette and node-tab-tab are simply wrappers similar to npm completion. When a special flag is seen, they simply emit a signal which can be received in the code

In other words, the process is:

1. Generate simple bash script which parses environment variables into "command line arguments" and calls git-meta again with a special flag
2. Get this bash script added to bash_completion, or manual install.
3. When user presses tab, bash script called git-meta, git-meta sees the special flag and instead of following code-paths, determines what are possible arguments and returns them to stdout