New bash tab completions for cargo and rustc

#1

After installing Rust on OS X via the dmg I had trouble getting the bash autocompletion to work (perhaps I should have used brew install instead).

Anyway I went ahead and made my own autocompletions. In case it’s useful to anyone else it’s at https://github.com/arikast/askbash

I’m new to Rust so my definitions were just based on what was displayed by the -h help pages. If anything seems off let me know and I’ll fix.

#2

It would be cool if the arguments to --bin, --test, --feature, etc could be completed too. Some of these will require parsing the manifest so they’ll need cooperation from cargo (or a custom subcommand).