Add support for tab completion in bash.

Summary:
From https://github.com/facebook/buck/pull/54.

When the bash_completion script is loaded, the user
can use the tab key to automatically complete the name of the
`buck command`, or if there are multiple commands beginning with
the same letter(s) suggest commands to use.

Test Plan:
Install the completion script:

  $ ./scripts/bash_completion

Suggestion of all available commands:

  $ buck
  audit build cache clean install project targets test uninstall

Suggestion of available commands with given starting letter:

  $ buck c
  cache clean

Completion of command with given starting letter

  $ buck b

("b" is auto-completed to "build")
1 file changed
tree: b7250c4fbfaf586de0735918bc71865068c955d4
  1. .idea/
  2. bin/
  3. config/
  4. docs/
  5. lib/
  6. plugin/
  7. pmd/
  8. scripts/
  9. src/
  10. test/
  11. testdata/
  12. third-party/
  13. .buckconfig
  14. .classpath
  15. .gitignore
  16. .project
  17. buck.iml
  18. build.xml
  19. DEFS
  20. LICENSE
  21. README.md
README.md

Buck

Buck is an Android build tool. To see what Buck can do for you, check out the documentation at http://facebook.github.io/buck/.

Installation

To build Buck, run the following:

git clone git@github.com:facebook/buck.git
cd buck
ant
./bin/buck --help

License

Apache License 2.0