benhoskings/babushka — pull request #295 by ecin (2013-11-18 20:22:50+00:00)
Title: Allow homebrew to install tapped packages.

Homebrew has the concept of "taps": repositories with custom formulas.
These formulas live in /usr/local/Library/Taps, instead of the
usual /usr/local/Library/Formula.

This commit checks for the presence of tapped formulas, to allow for:

```ruby
# Without this commit, babushka would be unable to find and install this package
dep do "apple-gcc42", :template => "bin" do
requires "homebrew-dupes.tap"
installs "homebrew/dupes/apple-gcc42"
end
```

Note taps still need to be installed before babushka will find
them:

```ruby
dep "homebrew-dupes.tap" do
requires "homebrew"

TAPS_DIR = "/usr/local/Library/Taps"

met? do
"#{TAPS_DIR}/homebrew-dupes".p.exists?
end

meet do
shell "mkdir -p #{TAPS_DIR}"
log_shell "Brewing Homebrew Dupes tap", "homebrew tap
homebrew/dupes"
end
end
```